Magnetic Properties and Magnetoresistance Effect in Evaporated NiFeCo Films

The anisotropic magneto-resistance (MR) ratio and magnetic anisotropy field H
k
have been examined for (Ni
0.82
Fe
0.18
)
100-x
Co
x
and Ni
82
Fe
18-x
Co
x
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 (Ni
0.82
Fe
0.18
)
100-x
Co
x
is almost constant regardless of changes in the Co concentration. The MR ratio for the Ni
82
Fe
18-x
Co
x
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 H
k
increases as the Co concentration is increased, and is not changed by annealing. The increase in the MR ratio for Ni
82
Fe
18-x
Co
x
films due to annealing is related to inhomogeneous strain and lattice defects. For Ni
82
Fe
12
Co
6
film, an MR ratio of 5.1% and an H
k
of 7.0 Oe were obtained, making such film suitable for application in MR heads.