New experiments on origin of anisotropy in Permalloy films

Abstract

A series of new experiments has been performed to determine the origin of the uniaxial anisotropy in Permalloy films. By means of a double magnetic shield enclosing the vacuum system, it was possible to deposit films in extremely small ambient fields (10−6 to 10−3 oersted). It was found that for deposition field strengths higher than about 10−1 oersted, the anisotropy constant and the squareness of the hysteresis loop are essentially invariant with respect to the value of the deposition field. However, forH d <10−1 oersted, both the anisotropy and squareness of the loop decreases dramatically. From these experimental results, it appears that both the anisotropic Fe-pair orientation and anisotropic imperfection-alignment are deposition-field induced.