A disk drive system having a spin valve (SV) magnetoresistive (MR) sensor having four leads, two leads for providing sense current to an SV element and two leads for providing current to an asperity compensation layer (ACL). The SV element as well as the hard bias layers are electrically insulated...http://www.google.de/patents/US5793207?utm_source=gb-gplus-sharePatent US5793207 - Disk drive with a thermal asperity reduction circuitry using a spin valve sensor 
