Abstract
The induced anisotropy in thin Ni79Fe21 films was investigated. The value of the induced anisotropy field Hk was found to decrease as the film thickness decreased, particularly below 20 nm, even after an adequate annealing procedure with a magnetic field. The value of Hk at 3 nm was found to be nearly half that at 200 nm. Almost the same thickness dependence of Hk was found to exist in both Ni77Fe23 and Ni81Fe19 films, except for slight differences in the absolute magnitude of Hk, depending on the composition. A series of CoZrNb amorphous films showed a qualitatively similar thickness dependence of Hk. On the other hand, the easy axis of the Ni79Fe21 films thinner than 20 nm was switched to the field direction by annealing with a magnetic field perpendicular to the easy axis of the as-deposited films, even at a low annealing temperature of 220°C. The absolute values of Hk in the 3 and 5 nm films after annealing were nearly as large as in the as-deposited films. It is likely that the rearrangement of atom pairs can easily occur in the surface region, resulting in the switching of the easy axis to the annealing field direction in very thin films.
