Analytic solution for magnetic orientation between grains

Abstract

Transmission electron microscopy experiments have shown that CoCrTa films for hard disk drives experience chromium segregation at grain boundaries. The resultant changes in the ferromagnetic parameters of the material together with the variation in the anisotropy direction from grain to grain are determining factors governing its magnetic behavior. In this paper, the case of two grains, differing in the direction of their magnetic anisotropy and possessing a change in their material content at the interface which we model by a Gaussian distribution, is solved analytically. Effects due to the diffuse interface such as localized regional changes in the anisotropy, exchange energy, and magnetic moment are included using perturbation theory. One of the outputs is the profile of the magnetization orientation in the inhomogeneous medium-thus yielding the smoothness and extent of the change. Such knowledge, in addition to its intrinsic scientific interest, paints the direction, both for large scale computer calculations and for media improvement.