Magnetoresistive sensors based on Ni/sub 81/Fe/sub 19//Ag multilayers

Because of their good magnetoresistive properties and thermal stability, sputtered NiFe/Ag multilayers (MLs) produce sensors with attractive characteristics. Thermal treatments up to 280 degrees C are 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 are made from these MLs using a microtechnology process. They are tested by reading magnetic tracks on a hard magnetic disk. Their performance is compared with sensors based on classical anisotropic MR in ferromagnetic 3-D alloys. The signal is found to be about ten times greater with this new ML than with sensors based on NiFe or NiFeCo alloys.<
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