Magnetic Properties and Magnetoresistance Effect in Evaporated NiFeCo Films

The anisotropic magneto-resistance (MR) ratio and magnetic anisotropy field Hk have been examined for (Ni0.82Fe0.18)100-xCox and Ni82Fe18-xCox evaporated films, both as-prepared and after annealing at 320°C for two hours, to evaluate their usefulness as MR head materials. The MR ratio of the (Ni0.82Fe0.18)100-xCox is almost constant regardless of changes in the Co concentration. The MR ratio for the Ni82Fe18-xCox films increases as the Co concentration increases, and after annealing the MR ratio rises up to 5% in the range of Co concentrations above 6 at%. The Hk increases as the Co concentration is increased, and is not changed by annealing. The increase in the MR ratio for Ni82Fe18-xCox films due to annealing is related to inhomogeneous strain and lattice defects. For Ni82Fe12Co6 film, an MR ratio of 5.1% and an Hk of 7.0 Oe were obtained, making such film suitable for application in MR heads.