Induced uniaxial magnetic anisotropy and film magnetostriction in very thin permalloy films

The induced uniaxial anisotropy field H/sub k/ in very thin films sandwiched by Ta or Cu layers was investigated. The value of H/sub k/ of the Ta/Cu/Ni/sub 79/Fe/sub 21//Cu/Ta film decreases as film thickness decreases below 20 nm, even after an annealing procedure in a magnetic field. This H/sub k/ reduction is similar to that of the Ta/Ni/sub 79/Fe/sub 21//Ta films, indicating that the H/sub k/ reduction is independent of surface energy and/or crystal structure of seed layers. The value of film magnetostriction /spl lambda//sub p-p/ of the Ta/NiFe/Ta films gradually increases as the thickness decreases, which is coincident with the reduction of H/sub k/. However, the increase of the /spl lambda//sub p-p/ values, by decreasing Ni concentration or annealing the films, resulted in conflicting H/sub k/ values. These results indicate that the H/sub k/ reduction in thin films is not simply caused by the magnetostrictive effect.