Theory of anisotropy skew in magnetostrictive thin films

Abstract

In magnetostrictive thin films, distinctive types of anisotropy skew patterns are found. These patterns depend on (i) the sign of the film's magnetostriction constant and (ii) the coefficient of thermal expansion of the film relative to that of its substrate. It is shown that these effects can be explained by the presence of thermal gradients in the film-substrate structure during and following the deposition process. Using the theory of magnetostrictively induced anisotropy in thin films, expressions for the variation in anisotropy field and easy-axis direction due to temperature gradients are derived and compared with those found experimentally. In order to restrict magnetostrictively induced easy-axis skews to ±0.5°, temperature gradients must be less than 0.5°K/cm.