Magnetic Properties and Magnetoresistance Effect in Evaporated NiFeCo Films

Abstract

The anisotropic magnetoresistance (MR) ratio and magnetic anisotropy field H_K have been examined for (Ni_0.82Fe_0.18)_100-x Co_x and Ni₈₂Fe_18-xCo_x evaporated films and those annealed at 320°C for 2 hours, to evaluate their usefulness as MR head materials. For the (Ni_0.82Fe_0.18)_100-x Co_x films, MR ratio is almost constant regardless of change in Co concentration. For the Ni₈₂Fe_18-xCo_x films, MR ratio increases as the Co concentration increases. Furthermore, MR ratio after the annealing raises to 5% in the Co concentration range greater than 6 wt%. H_K increases as the Co concentration increases, and is not changed by the annealing. The increase in MR ratio by the annealing for the Ni₈₂Fe_18-xCo_x films is related to inhomogeneous strain and lattice defects. For Ni₈₂Fe₁₂Co₆ film, 5.1% MR ratio and 7.8Oe H_K were obtained. These values seem appropriate for application to MR heads.