WO2000022612A1 - Capteur magnetique, tete magnetique, codeur magnetique et entrainement de disque dur - Google Patents
Capteur magnetique, tete magnetique, codeur magnetique et entrainement de disque dur Download PDFInfo
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- WO2000022612A1 WO2000022612A1 PCT/JP1999/005568 JP9905568W WO0022612A1 WO 2000022612 A1 WO2000022612 A1 WO 2000022612A1 JP 9905568 W JP9905568 W JP 9905568W WO 0022612 A1 WO0022612 A1 WO 0022612A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
- G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
- G11B5/3903—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects using magnetic thin film layers or their effects, the films being part of integrated structures
- G11B5/3906—Details related to the use of magnetic thin film layers or to their effects
- G11B5/3909—Arrangements using a magnetic tunnel junction
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y25/00—Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
- G01R33/09—Magnetoresistive devices
- G01R33/098—Magnetoresistive devices comprising tunnel junctions, e.g. tunnel magnetoresistance sensors
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/012—Recording on, or reproducing or erasing from, magnetic disks
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
- G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
- G11B5/3903—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects using magnetic thin film layers or their effects, the films being part of integrated structures
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/127—Structure or manufacture of heads, e.g. inductive
- G11B5/33—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only
- G11B5/39—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects
- G11B2005/3996—Structure or manufacture of flux-sensitive heads, i.e. for reproduction only; Combination of such heads with means for recording or erasing only using magneto-resistive devices or effects large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B2220/00—Record carriers by type
- G11B2220/20—Disc-shaped record carriers
- G11B2220/25—Disc-shaped record carriers characterised in that the disc is based on a specific recording technology
- G11B2220/2508—Magnetic discs
- G11B2220/2516—Hard disks
Definitions
- the present invention relates to a magnetic sensor, a magnetic head, a magnetic encoder, and a hard disk device, and more specifically, to a magnetic sensor, a magnetic head, a magnetic encoder, and a hard disk device using a ferromagnetic tunnel junction.
- this tunnel phenomenon refers to a phenomenon in which particles having kinetic energy smaller than the potential barrier, such as electrons, can move through the potential barrier. This is a unique phenomenon that cannot be explained in classical mechanics, but can be explained in quantum mechanics.
- the wave function of the particle travels outside the barrier while attenuating the inside of the potential barrier, and travels as a traveling wave unless the amplitude of the wave function is zero even outside the barrier, so it can pass through the barrier.
- tunnel phenomena include the phenomenon that spontaneous particles are emitted from the nucleus due to the collapse, the phenomenon that electrons are emitted from the metal surface by applying a high voltage to the metal (field emission), and the high reverse direction at the pn junction of the semiconductor. It is known that when a bias is applied, electrons pass through the depletion layer. This is a very important quantum mechanical effect in practical use.
- a typical tunneling phenomenon used in electronic devices is that when a voltage is applied to the metal on both sides of the junction of “metal insulator Z metal”, a slight voltage is applied when the insulator is sufficiently thin. There is a phenomenon that current flows. This phenomenon is usually caused by the fact that the insulator does not conduct current, but when the thickness of the insulator is as small as several Angstroms (A) to several tens A, preferably several to several tens of A, This is a phenomenon that occurs due to the quantum mechanical effect, with a slight probability that electrons will pass through this insulator. The current at this time is called “tunnel current”, and the junction having such a structure is called “tunnel junction”.
- the film is used as an insulating barrier.
- the film is formed by oxidizing the surface layer of aluminum by an appropriate oxidation treatment such as natural oxidation, plasma oxidation, or thermal oxidation.
- the thickness of the oxide film can be controlled by adjusting the oxidation conditions according to the oxidation treatment used, so that the oxide film can have a desired thickness of several Angstroms (A) to several tens A. .
- the aluminum oxide formed in this manner is a very thin insulator and thus functions as a barrier layer in a tunnel junction.
- the metal on both sides of the oxide film is replaced with a ferromagnetic metal. It is called.
- the tunnel probability tunnel resistance
- the tunnel resistance can be controlled by changing the magnetization state of the magnetic layers on both sides by a magnetic field. Assuming that the relative angle between the magnetization directions of the magnetic layers on both sides is ⁇ , the tunnel resistance R can be expressed by the following equation.
- Rs represents the tunnel resistance when a saturation magnetic field is applied. At this time, the two magnetization directions on both sides are in the direction of the applied magnetic field. Represents the change in the tunnel resistance.
- one of the two magnetic layers has a fixed magnetization direction as a fixed-side magnetic layer, and the other magnetic layer has a fixed magnetic field as a free-side magnetic layer.
- the direction is weakly controlled so as to be orthogonal to the magnetization direction of the fixed magnetic layer.
- This phenomenon is caused by the polarization of the electrons inside the ferromagnetic material.
- electrons in a substance have an electron whose spin state is upward (up electron) and an electron whose spin state is downward (down electron). Since the same number of up electrons and dow electrons exist inside the nonmagnetic metal, the nonmagnetic metal as a whole does not exhibit magnetism. However, since the number of up electrons (Nup) and the number of down electrons (Ndown) are different inside the magnetic metal, the magnetism with the larger number of electrons (ie, up magnetism or d 0 wn magnetism).
- the rate of change of the tunnel resistance (AR / Rs) is expressed by the product of the polarizability of the magnetic layer (tunnel source), which is the electron source, and the polarizability of the tunnel destination as shown in the following equation. Is done.
- the polarizability P of the magnetic layer is expressed by the following equation.
- Ndown The number of down electrons inside the magnetic layer
- the polarizability P of the magnetic layer depends on the type of ferromagnetic layer metal, but some have a value close to 50% depending on the type. In this case, theoretically, the rate of change in tunnel resistance (R / R) In s), a resistance change rate of several tens% can be expected.
- the anisotropy magnetoresistance effect As the conventionally known magnetoresistance effect (MR), the anisotropy magnetoresistance effect (AMR) has a resistance change rate of about 0.6%, and the giant magnetoresistance effect (GMR) has a resistance change rate of several percent. % To more than 10%. Therefore, the rate of change in tunnel resistance is much higher than those of AMR and GMR, and application to magnetic heads, magnetic sensors, and the like is expected.
- a spin valve structure is known as a typical example using GMR as a magnetic head.
- the present applicant has already proposed a TMR (tunnel-MR) head in which the above-described ferromagnetic tunnel junction is applied to the spin valve structure.
- This spin valve structure employs a structure in which a magnetic metal layer is interposed between two magnetic layers and only the magnetization direction of one of the magnetic layers is fixed, so that the magnetic layer is covered with an antiferromagnetic layer.
- the ferromagnetic tunnel junction has a structure in which a thin oxide film is interposed between two ferromagnetic layers.
- FIG. 1A is a cross-sectional view illustrating a ferromagnetic tunnel structure.
- a spin-valve structure having a ferromagnetic tunnel junction typically has a lower electrode 2 formed on a silicon substrate 1 and a free-side magnet formed on the lower electrode, as shown in FIG. 1A, for example.
- an upper electrode 9 formed on the substrate.
- a lower layer 10 is constituted by the lower electrode 2, the free magnetic layer 3, and the first magnetic metal layer 4.
- the upper electrode 9 forms the upper layer 12.
- a barrier layer 11 composed of an insulating layer 5 is interposed between the lower layer 10 and the upper layer 12 to be separated.
- Each element of the spin valve structure is, for example, as follows.
- Substrate 1 is made of silicon.
- Each of the lower electrode 2 and the upper electrode 9 is made of a Ta film, and has a thickness of 50 It is about nm.
- the free side magnetic layer 3 and the fixed side magnetic layer 7 are each composed of a NiFe film, and have a thickness of about 17 nm.
- Each of the first and second magnetic metal layers 4 and 6 is made of a C0 film, and has a thickness of about 3.3 nm.
- Insulating layer 5, A] - A 1 2 0 3 film or et made, the film thickness is 1 is about 3 nm.
- the antiferromagnetic layer 8 is made of a FeMn film and has a thickness of about 45 nm.
- the first N i Fe film is one of the two ferromagnetic layers, and is called a free magnetic layer (free layer) 3 because its magnetization direction is not fixed.
- the A 1 -A 10 film sandwiched between the two C 0 films 4 and 6 provides a barrier layer 11 composed of a thin aluminum oxide film A] ⁇ film forming a ferromagnetic tunnel junction.
- the second N i Fe film is the other ferromagnetic layer, and is called a fixed-side magnetic layer (bind layer) 7 because its magnetization direction is fixed.
- the first magnetic metal layer 4 functions in the same manner as the free magnetic layer 3, and the second magnetic metal layer 6 functions in the same manner as the fixed magnetic layer 7.
- the FeMn film is for exchange-coupling with the fixed magnetic layer 7 to fix the magnetization direction of the fixed magnetic layer, and is called an antiferromagnetic layer (pinning layer) 8.
- FIG. 1B is a schematic diagram illustrating measurement of a resistance change of the magnetic sensor using the ferromagnetic tunnel structure shown in FIG. 1A.
- a current source 39 is connected between the upper layer 12 and the lower layer 10 so that a constant current flows.
- a voltage detector 40 is connected between the upper layer 12 and the lower layer 10 to detect a voltage change between both layers.
- a magnetic field for example, a signal magnetic field
- the tunnel resistance of the ferromagnetic tunnel structure shown in FIG. 1A changes, and this is detected by the voltage detector 40 as a change in voltage.
- FIG. 2 shows the magnetoresistance effect curve of the tunnel structure using such a spin valve structure.
- Fig. 2 shows that as the external magnetic field changes from ⁇ 50 oersted (Oe) to 110 (0e) ⁇ 0 (0e) ⁇ +10 (0e) ⁇ +50 (Oe). It shows an irreversible resistance change rate of about 0.0% ⁇ about 0.0% ⁇ about 10.0% ⁇ about 20.0%-about 20.0%.
- the tunnel structure with a spin valve structure as shown in Fig. 2 shows that the external magnetic field shows a substantially linear resistance change rate of about 0 to 20% in the range of 10 to +10 (0e). There was found. In the range of ⁇ 30 to +30 (O e), the resistance change rate is about 0% to 20%. Also, by converting this to data of logic "0" and "1", it can be used for digital logic circuits.
- the magnetostatic coupling from the fixed magnetic layer to the free magnetic layer becomes relatively strong,
- the magnetization direction of the free magnetic layer tends to be in an antiparallel state to the magnetization direction of the fixed magnetic layer, and it is difficult to easily rotate the magnetization direction.
- the sensitivity of the magnetoresistive element decreases.
- hard disk drives are widely used in electronic devices because of their high data read / write speed and large storage capacity.
- the size of the recording bit of the magnetic recording medium also decreases, so that the magnetic head needs to be miniaturized to cope with this, and the detection sensitivity needs to be increased. .
- GMR Gate Magneto-Resistance effect
- a magnetic head when a magnetic field is externally applied to a laminated film having a magnetic layer / non-magnetic layer / nonmagnetic layer structure, the electric resistance of the laminated film changes due to the difference in magnetization angle between the two magnetic layers. This phenomenon is a magnetic head utilizing the GMR effect.
- FIG. Figure 3 is a conceptual diagram illustrating the GMR effect.
- the laminated film 310 having the GMR effect has a structure in which the nonmagnetic layer 316 is sandwiched between the magnetic layer 314 and the magnetic layer 318. ! Indicates the magnetization angle of the magnetic layer 3 14, and 2 indicates the magnetization angle of the magnetic layer 3 18. Magnetic layer 3 1 4 are magnetized in the magnetization base-vector M!, Magnetic layer 3 1 8 is magnetized in a magnetic base-vector M 2.
- the magnetization angle of the magnetic layer 314 becomes 0!
- the magnetization angle of the magnetic layer 3 18 is, for example, 0 2 .
- R R S + 0.5 xAR (l-cos A 0)
- the MR ratio is about 5 to 10%.
- a structure called a spin valve is generally adopted.
- the spin valve structure is disclosed in Japanese Patent Application Laid-Open No. 4-35810.
- FIG. 4 is a cross-sectional view showing a laminated film having a spin valve structure.
- the laminated film 4 10 having a spin valve structure includes a magnetic layer 414, a non-magnetic layer 4 16, a magnetic layer 4 18, and an antiferromagnetic layer 420.
- the antiferromagnetic layer 420 is formed on the magnetic layer 418 in the laminated film 410 having the spin valve structure.
- the magnetization direction of the magnetic layer 418 in contact with the antiferromagnetic layer 420 is fixed by the antiferromagnetic layer 420.
- only the magnetization direction of the magnetic layer 4 14 freely rotates according to the magnetic field from the outside.
- the magnetic layer 418 is called a fixed layer because the magnetization direction is fixed, and the magnetic layer 414 is called a free layer because the magnetization direction rotates freely.
- FIG. 5 is a perspective view showing the operation principle of a magnetic head using a spin valve structure.
- the core layer 400 has a spin-valve structure composed of a free layer 4 14, a nonmagnetic layer 4 16, a fixed layer 4 18, and an antiferromagnetic layer 4 20. Terminals 402 are formed on both sides of the core 400.
- the track width d! Becomes narrower accordingly, it must be narrow core width d 2 of the head to the magnetic to correspond to the track width d.
- the core 4 0 0 causes electrical resistance summer small, the detection sensitivity thereby summer low. Therefore, when narrowing the core width d 2 must be lowered height h of the core 4 0 0.
- the magnetization direction between the signal detection surface 43 0 side of the core 400 and the upper portion of the core 400 is affected by the demagnetizing field. The change in the electrical resistance of the core 400 is reduced because it is difficult to change.
- the region surrounded by the ellipse is a region in which the magnetization angle 0, of the free layer 4 14 is a certain angle or more. As shown in FIG. 6, the region where the magnetization angle 0, of the free layer 4 14 is more than a certain value is small, and the magnetization angle is small.
- an object of the present invention is to provide a novel magnetic sensor, magnetic head, and encoder.
- Still another object of the present invention is to provide a magnetic head capable of coping with a high density of a magnetic recording medium and a hard disk drive using the magnetic head and having a large storage capacity.
- An object of the present invention is a magnetic sensor having a ferromagnetic tunnel junction, wherein a free layer whose magnetization direction rotates freely, and a barrier layer formed on the free layer and having a first region with a reduced thickness. And a free layer in a region corresponding to the first region functions as a sensor unit that senses an external magnetic field.
- the rotation of the magnetization of the free layer can be sufficiently ensured in the region corresponding to the first region, so that a magnetic sensor having good sensitivity can be provided.
- the barrier layer may be formed by oxidizing a surface of a metal. Further, in the above magnetic sensor, on the barrier layer A fixed layer formed on the fixed layer, and an antiferromagnetic layer formed on the fixed layer to fix the magnetization direction of the fixed layer.
- the free layer in a region where the fixed layer is not formed above may be bent so as to be away from the fixed layer.
- the above object is achieved by a magnetic head having the above magnetic sensor. Thereby, a magnetic head having good sensitivity can be provided.
- the above object is achieved by a magnetic encoder characterized by having the above magnetic sensor.
- a magnetic encoder having good sensitivity can be provided.
- the above object is to provide a free layer in which the magnetization direction rotates freely, and a fixed layer in which the magnetization direction is fixed by an adjacent antiferromagnetic layer which faces one surface of the free layer via a barrier layer.
- the free layer may be connected to the member having high magnetic permeability in a region separated from the signal detection surface. Further, in the magnetic head described above, the free layer may be connected to the member having a high magnetic permeability while being smoothly approached. In the above magnetic head, the member having the high magnetic permeability may be a shield layer formed separately from the ferromagnetic tunnel junction device. In the above-mentioned magnetic head, the thickness of the barrier layer near the edge of the fixed layer may be larger than the thickness of the barrier layer near the center of the fixed layer. Further, in the above magnetic head, the free layer may be formed wider in a region separated from the signal detection surface. In the above magnetic head, the fixed layer may not be exposed on the signal detection surface.
- the member having the high magnetic permeability may be connected to a ground.
- the free layer in a region not facing the fixed layer may be bent away from the fixed layer.
- the ferromagnetic tunnel junction element faces the free layer via another barrier layer formed on the other surface side of the free layer, and is adjacent to another antiferromagnetic layer. It may further have another fixed layer in which the magnetization direction is fixed.
- the above object is achieved by a hard disk device having the above magnetic head.
- a hard disk device having a large recording capacity can be provided.
- the above object is achieved by a disk array device having a plurality of the above hard disk devices.
- a disk array device having a large storage capacity can be provided.
- FIG. 1 is a diagram illustrating a ferromagnetic tunnel structure.
- FIG. 1A shows a layer configuration having a ferromagnetic tunnel structure
- FIG. 1B is a schematic diagram illustrating measurement of a resistance change of the ferromagnetic tunnel structure of FIG. 1A.
- FIG. 2 is a graph showing the magnetic field-resistance characteristics of the tunnel junction of FIG.
- FIG. 3 is a conceptual diagram illustrating the GMR effect.
- FIG. 4 is a cross-sectional view showing a laminated film having a spin valve structure.
- FIG. 5 is a perspective view showing the operation principle of a magnetic head using a spin valve structure.
- FIG. 6 is a schematic diagram showing the magnetization direction of the free layer when the recording bit approaches.
- FIG. 7 is a diagram illustrating a configuration of a spin valve element in which a tunnel junction is incorporated in a spin valve structure.
- FIG. 7A shows a spin valve element according to the present example
- FIG. 7B shows a previously proposed spin valve element as a comparative example.
- FIG. 8 is a diagram showing a configuration of the magnetic sensor according to the first embodiment of the present invention.
- FIG. 9 is a view (No. 1) explaining the first method of manufacturing the magnetic sensor in FIG.
- FIG. 10 is a view (No. 2) explaining the first method of manufacturing the magnetic sensor in FIG.
- FIG. 11 is a diagram (part 1) illustrating a second method of manufacturing the magnetic sensor in FIG.
- FIG. 12 is a view (No. 2) explaining a second method of manufacturing the magnetic sensor of FIG.
- FIG. 13A is a diagram illustrating a magnetic sensor
- FIG. 13B is a diagram illustrating an equivalent circuit of the magnetic sensor
- FIG. 13C illustrates a mask used in manufacturing the magnetic sensor.
- FIG. 14A is a diagram illustrating output characteristics of the magnetic sensor
- FIG. 14B is a diagram illustrating the operation principle of the magnetic sensor.
- FIG. 15A is an equivalent circuit used to explain the operation principle of the magnetic sensor
- FIG. 15B is a diagram showing output characteristics of the magnetic sensor.
- FIG. 16A is a diagram showing an actual magnetic encoder
- FIG. 16B is an enlarged view of a magnetic sensor of the magnetic encoder.
- FIG. 17 is a sectional view showing a magnetic head according to the second embodiment of the present invention.
- FIG. 18 is a schematic diagram showing the magnetization direction of the free layer when the recording bit approaches.
- FIG. 19 is a cross-sectional view showing another specific example (part 1) of the magnetic head according to the second embodiment of the present invention.
- FIG. 20 is a cross-sectional view showing another specific example (part 2) of the magnetic head according to the second embodiment of the present invention.
- FIG. 21 is a cross-sectional view showing another specific example (part 3) of the magnetic head according to the second embodiment of the present invention.
- FIG. 22 is a sectional view showing a magnetic head according to the third embodiment of the present invention.
- FIG. 23 is a side view showing a magnetic head according to the fourth embodiment of the present invention.
- FIG. 24 is a plan view showing a magnetic head according to the fifth embodiment of the present invention.
- FIG. 25 is a plan view showing another specific example of the magnetic head according to the fifth embodiment of the present invention.
- FIG. 7A shows a tunnel having a spin valve structure according to the present embodiment.
- FIG. 3 is a diagram showing a structure of a magnetic sensor employing a magnetic junction.
- FIG. 7B shows the structure of a magnetic sensor having a spin valve structure proposed earlier as a comparative example.
- a tunnel junction having a spin valve structure is interposed between a lower magnetic pole 2 and an upper magnetic pole 9.
- This spin valve structure has a layer configuration in which a barrier layer 11 is disposed between a lower layer 10 and an upper layer 12.
- the spin valve structure generally has at least a free magnetic layer and a first magnetic metal layer as a lower layer 10, and
- the layer 12 includes at least a second magnetic metal layer, a fixed magnetic layer, and a diamagnetic layer.
- An intermediate portion between these two magnetic metal layers is a barrier layer 11, A thin insulating layer is interposed.
- a sensor section 13 is formed in a region near the center of the spin valve structure.
- a signal magnetic field Hsig from a recording medium such as a magnetic disk is applied from below as viewed in the figure to rotate the magnetization of the free magnetic layer.
- the sensor section 13 for the signal magnetic field is formed in a part of a substantially central part of a tunnel junction having a spin valve structure (magnetic layer). Part of the part is limited to LX hs).
- the size of the region of the sensor unit 13 is substantially equal to the size (h ⁇ L) of the region of the magnetic layer of the magnetic sensor described with reference to FIG. 7B. Accordingly, in the magnetic sensor according to the present embodiment, the size of the magnetic layer is smaller than that of the conventional magnetic head of FIG. , Has become relatively large.
- the structure of the magnetic sensor having the previously proposed spin valve structure shown in FIG. 7B has a spin valve structure interposed between the lower magnetic pole 20 and the upper magnetic pole 90.
- the layer structure of this conventional spin valve structure is the same as that of the spin valve structure shown in FIG. 7A, with a barrier layer 110 interposed between the lower layer 100 and the upper layer 120. It has a layer configuration.
- the lower layer 100 and the upper layer 120 have the same layer configuration as described with reference to FIG. 7A.
- a signal magnetic field Hsi from a recording medium such as a magnetic disk is used as an external magnetic field.
- g is applied from below as seen in the figure and rotates the magnetization of the free magnetic layer.
- the sensor section 130 for the signal magnetic field Hsig is formed by a portion sandwiched between two insulating layers 150-5 and 150-2 (the entire magnetic layer, ie, h XL).
- the sizes of the sensor sections 13 and 130 are almost the same.
- the sensor part 13 of the embodiment is limited to a part of the magnetic layer part, whereas the sensor part 130 of the latter (comparative example) is the entire magnetic layer part. .
- the sensor unit 13 can be set at an arbitrary position within the range of the magnetic layer.
- the sensor unit 13 is set near the center of the magnetic layer where the magnetization of the free side magnetic layer (one of the lower layers 10) is the most rotationally slow.
- the sensor section 13 can be formed as close as possible to the measurement signal magnetic field of the magnetic layer.
- the sensor section 13 can be formed at a location where the magnetization direction of the magnetic layer can easily rotate.
- the rotation of the magnetization of each magnetic domain of the sensor section 13 is caused by the element height of the magnetic layer because the sensor section 13 is a part of the substantially central portion of the magnetic layer. It can rotate freely without being affected by the dimension in the h direction. That is, since the height hs of the sensor section 13 is a part of the height h of the magnetic layer, the magnetic domain freely rotates near the edge of the sensor section 13 in response to the external signal magnetic field H sig. it can. Further, since the size of the magnetic layer is large regardless of the size of the sensor portion, it is possible to reduce the influence of the element shape such as the demagnetizing field.
- FIG. 8 is a detailed cross-sectional view of the magnetic sensor of the present embodiment shown in FIG. 7A.
- the layer configuration of the magnetic sensor is composed of a substrate 1, a lower layer 10 formed on the substrate, a barrier layer 11 formed on the lower layer, and a layer formed on the barrier layer.
- the lower layer 10 has a lower electrode 2, a free magnetic layer (lower layer, free layer) 3, and a first magnetic metal layer 4 formed on the free magnetic layer.
- the barrier layer 11 has an insulating layer 5.
- the upper layer 12 includes a second magnetic metal layer 6 formed on the insulating layer, a fixed magnetic layer 7 formed on the second magnetic metal layer, and a fixed magnetic layer 7 formed on the second magnetic metal layer. And an upper electrode 9 formed on the antiferromagnetic layer.
- the insulating layer 5 has a region formed at a part of the central part thereof, which is formed to be relatively thinner than other parts. Therefore, the surface of the second magnetic metal layer 6 formed above the insulating layer 5 is flat, but the central portion of the second magnetic metal layer 6 corresponding to the thin central portion of the insulating layer 5 has It is thicker than the other parts and is convex downward.
- the dent formed in the insulating layer 5 is about several angstroms. This central recess
- the area corresponding to 16 forms the sensor portion 13 as described with reference to FIG. 7A.
- the substrate 1 is preferably made of a Si substrate on which a natural oxide film is formed.
- the lower electrode 2 is preferably made of a Ta film having a thickness of about 50 nm.
- the free magnetic layer 3 is preferably made of a NiFe film having a thickness of about 17 nm.
- the first magnetic metal layer 4 is preferably made of a Co film having a thickness of about 3.3 nm.
- the insulating layer 5 is composed of an oxide A1 film having a film thickness of several angstroms (A) to several tens of A. In this embodiment, the film thickness is about 1.3 nm in the concave portion 16 and the film thickness in other portions. It consists of an aluminum oxide coating of about 3.3 nm.
- the second magnetic metal layer 6, like the first magnetic metal layer 4, preferably has a thickness of about 3.
- the first and second magnetic metal layers 4 and 6 are free side because the polarizability of the Co film is higher than the polarizability of the adjacent Ni Fe film (free side magnetic layer 3 or fixed side magnetic layer 7). This is provided to achieve a high MR ratio by laminating a Co film on the magnetic layer 3 or the fixed magnetic layer 7.
- the fixed magnetic layer 7 preferably has a film thickness of about 17 nm, like the free magnetic layer 3.
- the antiferromagnetic layer 8 is preferably made of a FeMn film having a thickness of about 50 nm.
- the upper electrode 9, like the lower electrode 2, is preferably made of a film having a thickness of about 511111.
- This magnetic sensor is a TMR (tunnel MR) that applies a ferromagnetic tunnel junction to a spin valve structure.
- the C0 layers 4 and 6 which are magnetic metal layers, are interposed between two magnetic layers (ie, the free magnetic layer 3 and the fixed magnetic layer 7).
- the magnetic layer is covered with an antiferromagnetic layer 8.
- the ferromagnetic tunnel junction forms a thin oxide film 5 between the two ferromagnetic layers 3 and 7 (more specifically, between the first and second magnetic metal layers 4 and 6). It has a structure in which it is interposed and arranged as a barrier layer 11.
- the thickness of the sensor portion 13 of the insulating layer 5 is relatively thinner than the other insulating layer portions.
- the tunnel resistance R in the thickness direction of the insulating layer 5 largely depends on the thickness of the insulating layer as represented by the following equation.
- t is the thickness of the insulating layer
- the tunnel current 18 flows intensively in a region where the thickness of the insulating layer 5 is small. That is, the DC current flows from the upper electrode 9 to the lower electrode 2 substantially in the region of each layer from the antiferromagnetic layer 8 to the free magnetic layer 3 corresponding to the region 16 having a small thickness of the insulating layer 5. Flows through. As a result, only the region corresponding to the recessed region 16 having the reduced film thickness functions substantially as the sensor unit 13.
- the tunnel resistance R when the relative angle between the magnetization directions of the magnetic layers on both sides is set to 0, the tunnel resistance R can be expressed by Expression (1). That is, the magnetizations of the free magnetic layer 3 and the magnetic metal layer 4 are rotating in response to the external signal magnetic field Hsig, and the ton determined by the relative angle 0 of the magnetization direction of the magnetic metal layers 4 and 6 on both sides.
- the flannel resistance R changes.
- the tunnel resistance R can be detected as a voltage value.
- the magnetic sensor must detect the external signal magnetic field Hsig. Can be done.
- the sensor section 13 is formed in a partial region of the magnetic layer.
- the sensor portion 13 is formed near the center of the magnetic layer, and has the same size as the magnetic layer region of the magnetic sensor proposed earlier (that is, the sensor portion 130 in FIG. 7B). Is formed. Therefore, the sensor section 13 can be formed at an optimum position in the magnetic layer region.
- the sensor section 13 can be formed near the center of the magnetic layer.
- the sensor section 13 can be formed at a position as close as possible to the measurement signal magnetic field. As a result, in the free side magnetic layer 3, the magnetization can be easily rotated in each magnetic domain without being affected by the end of the magnetic layer.
- FIGS. 7A and 8 A method of manufacturing the magnetic sensor described with reference to FIGS. 7A and 8 will be described with reference to FIGS.
- the first manufacturing method will be described with reference to FIGS. 9A to 9C and the second manufacturing method will be described with reference to FIGS. 11A to 12C due to the difference in the method of forming the thin insulating layer region.
- 9A to 10C are diagrams for explaining the first manufacturing method successively.
- an Si substrate 1 having a native oxide film is prepared.
- a Ta film is formed to a thickness of about 50 nm by sputtering. This Ta film functions as the lower electrode 2 after completion of the device.
- a NiFe film is formed to a thickness of about 17 nm, and a Co film is formed to a thickness of about 3.3.
- the free magnetic layer (lower layer, free layer) 3 composed of a NiFe film and the first magnetic metal layer 4 composed of a C0 film function as a free layer.
- a resist 19 is applied to the sensor section 13, and then, on the resist 19 and the first magnetic metal layer 4, an AI film 5-functioning as an insulating layer 5 is formed.
- 0 is formed to a film thickness of about 2. O nm.
- the first aluminum oxide film 5 - to 1 i.e., A 1 - A 1 2 ⁇ 3 film.
- the resist 19 is removed.
- the aluminum oxide film functions as a tunnel barrier. It functions as a functional thin insulating film 5.
- an Al film is again formed to a thickness of about 1.3 nm.
- the surface of the A] film is oxidized by plasma oxidation to form a second aluminum oxide film 5-2.
- the insulating layer 5 formed of the first aluminum oxide film 5-1 and the second aluminum oxide film 5-2 has a thickness of about 1.3 nm in the sensor portion 13 and other portions. Forms an insulating layer with a thickness of about 3.3 nm.
- the partially thinned region (sensor portion) of the insulating layer 5 functions as a tunnel barrier after the device is completed.
- a NiFe film is formed to a thickness of about 17 nm on the Co film.
- a FeMn film is formed to a thickness of about 50 nm.
- portions other than the element portion are removed by ion milling, RIE (reactive ion etching), or the like, and insulating layers 15-1, 15-2 are added to the removed portions.
- RIE reactive ion etching
- insulating layers 15-1, 15-2 are added to the removed portions.
- a Ta film having a thickness of about 50 nm is formed on the insulating layers 15-1, 15-2 and the antiferromagnetic layer 8.
- This Ta film functions as an upper electrode 9 after completion of the device.
- the insulating layers 15-1, 15-2 are provided so that the upper electrode 9 and the lower electrode 2 do not come into contact with each other directly or through the edge of the element portion.
- the magnetic sensor manufactured as described above has an insulation made of aluminum oxide when a sense current (constant DC current) 17 flows from the upper electrode 9 to the lower electrode 2.
- the tunnel current passing through the film 5 intensively flows in a relatively thin portion, and this portion functions as the sensor unit 13. Since the thin portion of the oxide A1 film can be formed at an arbitrary position, the sensor portion 13 is provided at an arbitrary position in the magnetic layer, preferably at a center portion where the magnetic domain of the free magnetic layer 3 is most likely to rotate. The smooth rotation of the magnetic domain is ensured.
- FIGS. 11A to 12C are diagrams illustrating a second method of manufacturing the magnetic sensor continuously. It is. The second manufacturing method is different from the first manufacturing method in that a step of forming a thin insulating film is different.
- an Si substrate 1 having a native oxide film is prepared.
- a Ta film is formed to a thickness of about 50 nm using the Spack method.
- This Ta film functions as the lower electrode 2 after completion of the device.
- a NiFe film was formed to a thickness of about 17 nm, and a Co film was formed to a thickness of about 3.3 nm.
- the free magnetic layer 3 made of a NiFe film and the first magnetic metal layer 4 made of a Co film function as a free layer. Up to this stage, it is the same as the first manufacturing method.
- the resist 2 1 was applied to the sensor unit 1 3, then over the resist and the first magnetic metal layer 4, the first A 1 2 0 3 film 5-1 Approximately 2.0 nm film thickness.
- an A1 film was formed to a thickness of about 1.3 nm, and the surface of the A1 film was oxidized using plasma oxidation to form aluminum oxide. film and (second a 1 2 0 3 film) 5-2.
- the insulating layer 5 formed of the first aluminum oxide film 5-1 and the second aluminum oxide film 5-2 has a thickness of about 1.3 nm in the sensor section 13 and other layers. In this area, an insulating layer with a thickness of about 3.3 nm is formed.
- the partially thinned region (sensor portion) of the insulating layer 5 functions as a tunnel barrier after the device is completed.
- a Co film is formed as a second magnetic metal layer 6 on the thin insulating film 5 to a thickness of about 3.3 nm.
- a Ni 6 film 7 having a thickness of about 17 nm is formed on the second magnetic metal layer 6 as the fixed magnetic layer 7.
- a FeMn film having a thickness of about 50 nm is formed as an antiferromagnetic layer 8 on the fixed magnetic layer 7.
- the part outside the element site is removed by ion milling, RIE, etc., and the insulating layers 15-1, 15-2 are formed on the removed part. Thereafter, a Ta film is formed on the insulating layers 15-1, 15-2 and the antiferromagnetic layer 8 as an upper magnetic pole 9 to a thickness of about 50 nm.
- the magnetic sensor manufactured in this manner is sensed from the upper electrode 9 to the lower electrode 2.
- a constant current (constant DC current) 17 flows, the tunnel current passing through the insulating film 5 made of aluminum oxide intensively flows to the sensor portion 13 having a relatively thin film thickness. Function as a unit. Therefore, the relatively thin portion can be provided at an arbitrary position in the magnetic layer, preferably at the center where the magnetic domain of the free magnetic layer is most likely to rotate, and smooth rotation of the magnetic domain is secured. Is done.
- Magnetic sensors such as those described above are typically applicable to magnetic heads.
- a magnetic head a capacitive head (inductive head) is used for recording, a GMR head is used for reproduction, and a composite magnetic head that integrates both heads is used.
- a head has been developed and put into practical use.
- GMR heads typically employ a spin-valve structure (but no tunnel junction). Instead of such a composite type magnetic head GMR head, the above-described magnetic sensor having a spin valve structure having a tunnel junction can be used as it is.
- FIG. 13A is a diagram showing a magnetic sensor 50 used in the magnetic encoder according to the present embodiment.
- the magnetic sensor 50 has a power supply terminal V, a ground terminal GND, an output A terminal A-OUT, and an output B terminal B-OUT.
- a first ferromagnetic tunnel junction element TMR (tunnel-MR) 1 is connected between the power supply terminal V and the output A terminal A—OUT, and the power supply terminal V and the output B terminal
- a second ferromagnetic tunnel junction device TMR 2 is connected between B-0UT and a third ferromagnetic tunnel junction device TMR 3 is connected between the ground terminal GND and the output A terminal A-OUT.
- a fourth ferromagnetic tunnel junction device TMR4 is connected between the ground terminal GND and the output B terminal B-OUT.
- FIG. 13B is a diagram showing an equivalent circuit of the magnetic sensor 50 of FIG. 13A.
- a method of manufacturing the magnetic sensor shown in FIG. 13A will be briefly described. First, using a mask as shown in Fig. 13C, a NiFe film was formed to a film thickness of about 1 nm as the free magnetic layer, and then continuously formed as the first magnetic metal layer.
- A] was formed to a thickness of about 1.3 nm as an insulating layer, and the surface was oxidized.
- the oxidation treatment was performed by the plasma oxidation method described in the first manufacturing method and the second manufacturing method, and a thin oxide film was formed in the sensor portion, and a relatively thick oxide film was formed in other regions. Note that other oxidation treatments, for example, a natural oxidation method may be performed.
- the magnetic encoder can be manufactured by the same layer configuration and manufacturing process as the spin-valve magnetic sensor. Next, the operation of the magnetic encoder will be described.
- FIG. 14A is a diagram schematically showing a magnetic resistance curve of the magnetic encoder shown in FIG. 13A.
- the magnetization direction Mupper of the upper layer 12 of the ferromagnetic tunnel junction device TMR is perpendicular to the magnetization direction Mlower of the lower layer 10 so that the antiferromagnetic layer (F e Mn film) 8 fixed.
- the resistance value when the external magnetic field is zero is defined as R0.
- the magnetization direction Mlo When an external magnetic field is applied to the ferromagnetic tunnel junction device TMR in a direction opposite to the magnetization direction Mupper of the upper layer 12 (that is, the external magnetic field H), the magnetization direction Mlo was of the lower layer 10 rotates and the upper layer 12
- the resistance values of the ferromagnetic tunnel junction device TMR when the external magnetic field is 1 H, 0, and + H are RL, R0, RH, and these relationships are RL ⁇ R0 ⁇ RH.
- Figure 14A illustrates this relationship.
- FIG. 14B is a diagram for explaining the operation principle of this encoder.
- the magnetic sensor 50 including the magnetic field generating magnet 55 to be measured and the tunnel junction element TMR has a positional relationship as shown in the figure.
- the magnetic field generating magnet 55 is a slender magnetized body in which N poles and S poles are alternately magnetized, and the interval (magnetization cycle) between a pair of SN poles is represented by I.
- TMR1-TMR4 have a relation of relatively moving in the longitudinal direction of the magnet in the vicinity of the magnetic field generating magnet 55.
- the magnetic sensor 50 including the tunnel junction elements TMR1 to TMR4 is at the position shown in the sensor position [1].
- Each ferromagnetic tunnel junction device TMR is arranged at an interval of ⁇ / 4.
- the magnetic sensor 50 moves iZ4 parallel to the right as viewed in the figure and is at the position shown in the sensor position [2].
- the force shown in FIG. Note that the vicinity of the magnet 55 (that is, the position of the sensor [1]) is relatively translated in the longitudinal direction of the magnet. The same applies to sensor positions [3] and [4].
- the magnetic sensor 50 at the sensor position [2] is at the sensor position [3] after a certain period of time t, and moves parallel to the sensor position sensor positions [4],.
- Fig. 15A is a diagram corresponding to Fig. 13B. From this equivalent circuit, the voltage output VA and VB of the output A terminal and the output B terminal are divided into the voltage V at the output A terminal by TMR1 and TMR3. Since the output B pin divides the voltage V by TMR2 and TMR4, the output is as follows.
- V ⁇ TMR4 / (TMR2 + TMR4) V ⁇ RO / (RO + R0)... (6)
- TMRl RH
- TMR2 RO
- TMR3 RL
- TMR4 R0. Therefore, the voltage outputs VA and VB of the output A terminal and output B terminal are as follows.
- FIG. 15B is a diagram showing an output waveform of this sensor unit.
- FIG. 16 is a diagram showing an actual magnetic encoder using the operation principle described in FIG.
- This magnetic encoder has a rotating magnetized body 56 and a magnetic sensor 50 arranged in the vicinity thereof. Instead of making the magnetic field generating magnet 55 infinite, a rotating magnet 56 is actually used.
- the rotating magnet body 56 has a diameter of 10 mm and a shaft diameter of 5 mm, and 16 pairs of SN poles are radially arranged on the circumference thereof. At this time, the magnetization period; I is about 1.5 mm.
- the magnetic sensor 50 is positioned such that the center of the sensor is aligned with the center of the radially magnetized portion of the rotating magnetized body 56.
- the ferromagnetic tunnel junction elements TMR in parallel with the radially extending magnets of the rotating magnetized body 56, and so that the element intervals are ⁇ / 4.
- the angle formed by each element TMR is about 5.6.
- the distance between the centers of adjacent elements is 0.37 mm.
- Such a magnetic encoder can obtain an output waveform as described in FIG. 15B from each ferromagnetic tunnel resistance element TMR 5 of the magnetic sensor 50 by rotating the rotary magnet 56. That is, when the magnetic sensor 50 moves relative to the rotating magnetized body 56 by a magnetizing cycle; I, an output pulse for one cycle is generated.
- each ferromagnetic tunnel junction At the tunnel junction of the element TMR the sensor section can be formed at the optimum position in the magnetic layer region.
- the magnetization can be easily rotated in each magnetic domain without being affected by the end of the magnetic layer.
- a magnetic sensor having a good sensitivity, a magnetic head, and a magnetic sensor such as a magnetic encoder are generally used. Can be applied.
- FIG. 17 is a cross-sectional view showing the magnetic head according to the present embodiment.
- FIG. 17B is an enlarged sectional view of the ferromagnetic tunnel junction device of FIG. 17A.
- the magnetic head according to the present embodiment uses a ferromagnetic tunnel junction element 210 whose electric resistance changes in response to a change in an external magnetic field.
- the tunnel junction element 210 has a free layer 214, a barrier layer 216, a fixed layer 218, and an antiferromagnetic layer 220.
- the free layer 214 includes a 3-nm-thick NiFe layer 221 and a 3-nm-thick Co layer 224. Then, adjacent to the C o layer 224 of the free layer 2 1 4, barrier layer 21 6 made of A 1 2 0 3 layer having a thickness of 1 nm is formed.
- a fixed layer 2 18 of a 3 nm-thick Co layer 226 and a 3 nm-thick NiFe layer 228 is formed adjacent to the barrier layer 2 16.
- An antiferromagnetic layer 220 composed of a Ni0 layer is formed adjacent to the layer 18.
- shield layers 2 12 a and 2 12 b made of a NiFe layer are formed at a distance from the ferromagnetic tunnel junction device 210 and are shielded from the ferromagnetic tunnel junction device 210.
- layer 2 1 2 a, 2 non-magnetic layer 222 force consisting of a 1 2 0 3 layer is between 1 2 b, 'is formed.
- the lower side of the drawing is the signal detection surface 230 of the magnetic head.
- FIG. 1A shows a state where the recording bit 232 of the magnetic recording medium is close to the ferromagnetic tunnel junction element 210. Actually, a large number of recording bits 232 are formed in the magnetic recording medium, but are omitted in FIG. 17A.
- the magnetization direction of the free layer 214 rotates.
- the fixed layer 2 18 since the antiferromagnetic layer 220 is formed adjacently, the magnetization direction remains fixed.
- the free layer 214 extends in a direction away from the signal detection surface 230, and the extended free layer 214 The end is connected to the shield layer 212a.
- the free layer 2 14 is connected to the shield layer 2 12 a composed of a Ni Fe layer having a high magnetic permeability, the magnetic flux from the recording bit 2 32 4 will pass easily. Moreover, since the free layer 214 extends in a direction away from the signal detection surface 230, the effect of the demagnetizing field on the free layer 214 can be reduced. It is possible to increase the rotation angle of the magnetization direction of the magnetic field. Further, since the free layer 214 is gently connected to the shield layer 212a in a region separated from the signal detection surface 230, the influence of the demagnetizing field on the free layer 214 is further reduced. Can be reduced.
- FIG. 18 is a schematic diagram showing the calculation of the magnetization direction of the free layer when the recording bit approaches. Arrows indicate the magnetization direction. The region surrounded by the ellipse is a region in which the magnetization angle of the free layer is a certain angle or more. FIG. 18 shows the magnetization direction of the free layer in a range of about 20 m from the signal detection surface.
- the effect of a demagnetizing field occurs near the signal detection surface 430 and near the upper part of the core 400. Had been lost. Therefore, the magnetization angle S of the free layer 414 when the recording bit 332 approached was small, and it was difficult to obtain a high output.
- the change in the electrical resistance of the ferromagnetic tunnel junction device 210 when the recording bit 23 comes close can be made larger than that of the conventional magnetic head, whereby High detection sensitivity can be obtained.
- the free layer extends in a direction away from the signal detection surface, and the end of the extended free layer is connected to the shield layer having high magnetic permeability.
- the effect of the magnetic field can be reduced.
- the influence of the demagnetizing field in the vicinity of the junction region between the free layer and the fixed layer can be reduced, so that the rotation angle of the magnetization direction in the junction region can be increased, and when the recording bit approaches, The change in electric resistance can be increased. Therefore, even when the width of the junction region is narrowed, a magnetic head having sufficiently high detection sensitivity can be provided, and it is possible to cope with a high recording density of a magnetic recording medium.
- FIG. 19 is a sectional view showing a magnetic head according to this example.
- FIG. 19B is an enlarged sectional view of the ferromagnetic tunnel junction device of FIG. 19A.
- the region where the influence of the demagnetizing field is small is the junction region 234 between the fixed layer 2 18 and the free layer 2 14.
- the rotation angle of the magnetization direction is reduced due to the effect of the demagnetizing field.
- the thickness of the barrier layer 216 is made thin enough to cause a tunnel junction, and the thickness of the barrier layer 216 in the region near the edge of the fixed layer 218 is increased.
- the region excluding the edge of the fixed layer 2 18, that is, the region where the influence of the demagnetizing field is small becomes the junction region 2 34.
- the change in electric resistance can be increased.
- the region where the influence of the demagnetizing field is small is set as the bonding region, a magnetic head having high detection sensitivity can be provided.
- FIG. 20 is a cross-sectional view showing a magnetic head according to this example.
- the magnetic head according to the second embodiment shown in FIG. 1A is the same as the magnetic head according to the second embodiment shown in FIG.
- the fixed layer 2 18 a is composed of a laminated film of the N i Fe layer 2 28, the Co layer 226, the Ru layer 236, and the Co layer 240, Antiferromagnetic coupling is formed between the o-layer 226 and the Co-layer 240. Accordingly, it is possible to suppress a magnetic field from being applied from the fixed layer 2 18 a to the free layer 2 14, and it is possible to suppress a shift of the bias point of the free layer 2 14. .
- the fixed layer is formed of a laminated film of the NiFe layer 228, the Co layer 222, the Ru layer 236, and the Co layer 240, the Co layer 226
- An anti-ferromagnetic coupling can be formed between the Co layer and the Co layer 240, so that the magnetic field from the fixed layer to the free layer can be suppressed. Therefore, it is possible to prevent the bias point of the free layer from shifting.
- FIG. 21 is a cross-sectional view showing a magnetic head according to this example.
- FIG. 21B is an enlarged sectional view of the ferromagnetic tunnel junction device of FIG. 21A.
- the fixed layer 218 is not exposed to the signal detection surface 230 and the end of the free layer 214 is connected.
- the shield layer 2 1 2a is connected to the ground.
- the magnetic recording medium is grounded.
- the connection makes the potential between the free layer 214 and the magnetic recording medium equal. Can be. Therefore, it is possible to prevent a potential difference from occurring between the free layer 214 and the magnetic recording medium, thereby preventing discharge from occurring from the free layer 214 toward the magnetic recording medium. . Therefore, in this specific example, it is possible to prevent the recording information of the recording bit from being destroyed by the discharge.
- the bonding area 2 34 between the fixed layer 2 18 and the free layer 2 14 is separated from the signal detection surface 230, even if the bonding surface 230 is worn, it is fixed. It is rare that the layer 2 18 and the free layer 2 14 are worn down to the joint area 2 3 4. Therefore, it is possible to prevent the joint region 234 between the fixed layer 218 and the free layer 214 from being reduced.
- the signal detection surface 230 can be brought into contact with the magnetic recording medium to be used as a contact-type magnetic head.
- the fixed layer is not exposed on the signal detection surface, it is possible to prevent discharge from occurring even when a potential difference occurs between the fixed layer and the magnetic recording medium. .
- the free layer exposed on the signal detection surface is connected to the ground via the shield layer, the potential between the free layer and the magnetic recording medium is established by connecting the magnetic recording medium to the ground. Can be made equal. Therefore, it is possible to prevent a potential difference between the free layer and the magnetic recording medium, and to prevent a discharge from being generated from the free layer toward the magnetic recording medium. It is possible to prevent the recorded information of the bird from being destroyed.
- the present invention can be applied to a contact-type magnetic head that uses a signal detection surface in contact with a magnetic recording medium.
- FIG. 22 is a cross-sectional view showing the magnetic head according to the present embodiment.
- the same components as those of the magnetic head according to the second embodiment shown in FIGS. 17 to 21 are denoted by the same reference numerals, and description thereof will be omitted or simplified.
- the magnetic head according to the present embodiment is characterized in that the ferromagnetic tunnel junction device 210a has two ferromagnetic tunnel junctions.
- the barrier layer 2 16 a substantially similar to the barrier layer 2 16 is formed plane-symmetrically around the free layer 2 14, and the fixed layer 2 18 substantially similar to the fixed layer 2 18 b is formed symmetrically with respect to the free layer 2 14.
- the antiferromagnetic layer 2200 is substantially the same as the antiferromagnetic layer 220 and is formed to be plane-symmetric with respect to the free layer 214.
- the magnetization direction of the fixed layer 218 becomes similar to the magnetization direction of the fixed layer 218b.
- the ferromagnetic tunnel junction 2 ⁇ 0a has two ferromagnetic tunnel junctions, high detection sensitivity can be realized by adding the outputs of these two ferromagnetic tunnel junctions.
- FIG. 23 is a side view of the magnetic head according to the present embodiment.
- the same components as those of the magnetic head according to the second or third embodiment shown in FIGS. 17 to 22 are denoted by the same reference numerals, and description thereof will be omitted or simplified.
- the magnetic head according to the present embodiment is characterized by the shape of the free layer 214a. That is, the width of the free layer 2 14 a is fixed in the vicinity of the signal detection surface 230 or in the vicinity of the junction area 2 34 between the fixed layer 2 18 and the free layer 2 14 a. 8 is slightly wider than the width of, but gradually widens as it moves away from the signal detection surface 230. It's dead. Further, further away from the signal detection surface 230, the width of the free layer 214a becomes very wide.
- the magnetization direction of the free layer is inclined in the longitudinal direction of the free layer even when no magnetic field is applied from the outside.
- the shape is as shown in FIG. 23, the magnetization direction of the free layer 2 14 a near the junction region 2 34 in a state where no magnetization is applied from the outside is given. It can be prevented from tilting. Thereby, when a magnetic field is applied from the outside, the magnetization direction of the free layer 214a is sufficiently rotated in the vicinity of the junction region 234, so that a magnetic head with high detection sensitivity can be provided. It becomes possible.
- the width of the free layer is formed wider as the distance from the signal detection surface is increased, and the width of the free layer is extremely wide in a region separated from the signal detection surface. In the state where no is added, it is possible to suppress the magnetization direction of the free layer from being inclined near the junction region. Therefore, when a magnetic field is applied from the outside, the rotation angle of the magnetization direction of the free layer near the junction region can be increased, and a magnetic head with high detection sensitivity can be provided.
- FIG. 24 is a plan view of the magnetic head according to the present embodiment as viewed from the signal detection surface side.
- the same components as those of the magnetic head according to the second to fourth embodiments shown in FIGS. 17 to 23 are denoted by the same reference numerals, and description thereof will be omitted or simplified.
- the magnetic head according to the present embodiment has a structure in which the free layer 2 14 b in the region excluding the junction region 2 34 between the fixed layer 2 18 and the free layer 2 14 b is formed. It is characterized in that it is bent away from the fixed layer 218.
- the free layer 2 1 4 b in the area other than the junction area 2 3 4 between the fixed layer 2 18 and the free layer 2 1 4 b is bent away from the fixed layer 2 18 so that the height of the magnetic recording medium Even if the distance between the tracks becomes narrower due to the increase in the recording density, it is possible to reduce the influence of the magnetic field from the recording bits of the adjacent tracks.
- the recording bit of the adjacent track is The effect of the magnetic field from the magnetic field can be reduced. This makes it difficult to receive the influence of the magnetic field from the recording bit of the adjacent track, so that it is possible to cope with an increase in the recording density of the magnetic recording medium.
- FIG. 25 is a plan view of the magnetic head according to this example as viewed from the signal detection surface side.
- the free layer 2 1 4 c force ⁇ fixed layer 2 1 in the region excluding the junction region 2 3 4 between the fixed layer 2 18 and the free layer 2 14 c
- the bent free layer 2 14 c is bent further away from the shield layer 2 12 a force.
- the distance between the shield layer 212a and the shield layer 212b can be reduced, so that a portion for detecting a signal can be miniaturized, thereby further increasing the recording density of the magnetic recording medium. Can be handled.
- the free layer in the region other than the junction region between the fixed layer and the free layer is bent away from the fixed layer, and the bent free layer further moves away from the shield layer. So bent.
- the distance between the shield layers can be reduced, so that a portion for detecting a signal can be miniaturized, and a higher recording density of a magnetic recording medium can be accommodated.
- the lower layer 10 functioning as a free layer extends in a direction away from the signal detection surface, and an end of the extended lower layer 10 is connected to a shield layer having high magnetic permeability. May be.
- the influence of the demagnetizing field on the sensor unit 13 can be further reduced, so that the detection sensitivity can be further improved.
- the lower layer 10 may be formed as a free layer 214b shown in FIG. That is, the lower layer 10 may be bent away from the upper layer 12 in an area other than the sensor section 13. As a result, the influence of the magnetic field from the recording bit of the adjacent track can be reduced, so that it is possible to cope with a higher recording density of the magnetic recording medium.
- a magnetic head using the magnetic sensor according to the first embodiment is It is also possible to apply to an apparatus. By using such a highly sensitive magnetic sensor, it is possible to cope with a higher recording density of a magnetic storage medium.
- the free layer is connected to the shield layer.
- the free layer may be appropriately connected not only to the shield layer but also to a magnetic material having high magnetic permeability.
- the magnetic head has been described.
- a hard disk drive can be provided using the magnetic head as described above.
- a disk array device can be provided by using a plurality of such hard disk devices.
- the NiFe layer or the Co layer is used as the material of the free layer or the fixed layer, but the material of the free layer or the fixed layer is the NiFe layer or the Co layer.
- the present invention is not limited to this, and any other layer that can realize a ferromagnetic tunnel junction can be used as the free layer or the fixed layer.
- the present invention is suitable for a magnetic sensor, a magnetic head, a magnetic encoder, and a hard disk drive, and particularly, a magnetic sensor, a magnetic head, a magnetic encoder, and a high-density magnetic recording medium capable of realizing good sensitivity.
- the present invention is useful for a magnetic head capable of coping with the trend and a hard disk drive having a large storage capacity using the magnetic head.
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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DE19982238T DE19982238T1 (de) | 1998-10-12 | 1999-10-08 | Magnetsensor, Magnetkopf, Magnetcodierer und Festplattenvorrichtung |
KR1020007006051A KR100631355B1 (ko) | 1998-10-12 | 1999-10-08 | 자기 센서, 자기 헤드, 하드 디스크 장치, 및 디스크 어레이 장치 |
US09/581,468 US7199985B1 (en) | 1998-10-12 | 2000-06-12 | Magnetic sensor, magnetic head, magnetic encoder and hard disk device |
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JP28978198A JP4104748B2 (ja) | 1998-10-12 | 1998-10-12 | 磁気センサ、磁気ヘッド及び磁気エンコーダ |
JP10/289781 | 1998-10-12 | ||
JP10/308989 | 1998-10-29 | ||
JP30898998A JP3260708B2 (ja) | 1998-10-29 | 1998-10-29 | 磁気ヘッド及びハードディスク装置 |
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US09/581,468 Continuation US7199985B1 (en) | 1998-10-12 | 2000-06-12 | Magnetic sensor, magnetic head, magnetic encoder and hard disk device |
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WO2000022612A1 true WO2000022612A1 (fr) | 2000-04-20 |
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US (1) | US7199985B1 (ja) |
KR (1) | KR100631355B1 (ja) |
CN (2) | CN1160707C (ja) |
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US7901802B2 (en) | 2006-03-15 | 2011-03-08 | Seagate Technology Llc | Magnetic recording medium for perpendicular magnetic recording |
JP4232808B2 (ja) * | 2006-09-19 | 2009-03-04 | 日立金属株式会社 | 磁気エンコーダ装置 |
FR2929041B1 (fr) * | 2008-03-18 | 2012-11-30 | Crocus Technology | Element magnetique a ecriture assistee thermiquement |
US9972352B2 (en) * | 2009-08-19 | 2018-05-15 | Seagate Technology Llc | Antiferromagnetic coupling layers |
US20110101964A1 (en) * | 2009-11-05 | 2011-05-05 | Udo Ausserlechner | Magnetic Encoder Element for Position Measurement |
US9196825B2 (en) * | 2013-09-03 | 2015-11-24 | Taiwan Semiconductor Manufacturing Co., Ltd. | Reversed stack MTJ |
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- 1999-10-08 KR KR1020007006051A patent/KR100631355B1/ko not_active IP Right Cessation
- 1999-10-08 CN CNB2004100016519A patent/CN1259650C/zh not_active Expired - Fee Related
- 1999-10-08 WO PCT/JP1999/005568 patent/WO2000022612A1/ja active IP Right Grant
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Also Published As
Publication number | Publication date |
---|---|
CN1160707C (zh) | 2004-08-04 |
US7199985B1 (en) | 2007-04-03 |
DE19982238T1 (de) | 2001-02-15 |
CN1523574A (zh) | 2004-08-25 |
CN1288558A (zh) | 2001-03-21 |
CN1259650C (zh) | 2006-06-14 |
KR100631355B1 (ko) | 2006-10-09 |
KR20010032759A (ko) | 2001-04-25 |
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