MAGNETORESISTIVE SENSORS BASED ON NI81FE19/AG MULTILAYERS

Because of their good magnetoresistive properties and thermal stability sputtered NiFe/Ag multilayers (ML) have been made to produce sensors with attractive characteristics. Thermal treatments up to 280-degrees-C have been carried out. They lead to improved sensitivity; the magnetoresistance (MR) ratio remains practically constant while the saturation field decreases from 24 kA/m to 6 kA/m after annealing. Sensors have been made from these ML using a microtechnology process. They were tested by reading magnetic tracks on a hard magnetic disc. Their performance has been compared with sensors based on classical anisotropic MR in ferromagnetic 3d alloys. The signal is found to be about ten times greater with this new ML than with sensors based on NiFe or NiFeCo alloys.