Magnetic Properties of Magnetoresistive Element Annealed in Magnetic Field

The magnetoresistive (MR) effect and anisotropy field Hk in NiFe thin films, annealed in dc and rotating magnetic fields, were studied. In large MR elements, Hk decreased with annealing at temperatures up to 300°C due to stress relaxation. When the annealing temperature exceeded 350°C, the ¿¿/¿ vs. H curves measured along both the hard and easy axes of magnetization showed a large dispersive hysteresis. This resulted in a decrease in ¿¿/¿. In MR elements consisting of a narrow stripe, on the other hand, the magnetoresistive and magnetic properties of the NiFe film changed hardly at all for temperatures up to 500°C, because they were controlled by the shape magnetic anisotropy. An MR head with a magnetic yoke consisting of amorphous CoNbZr was fabricated. The MR head was annealed in dc and rotating magnetic fields in order to obtain a high yoke permeability. A satisfactory MR characteristic was attained for the NiFe film in the head.