Perpendicular Anisotropy in Polycrystalline Ni-Fe Thin Films

Abstract

A magnetostatic model for perpendicular anisotropy (i.e., the anisotropy resulting from the rotation of the magnetization out of the plane of the film) is presented on the basis of columnar grain structure in ferromagnetic thin films. The calculation shows that the anisotropy constant is proportional to the square of saturation magnetization and the proportionality factor should decrease with increasing ratio (d/D) of the grain boundary layer thickness to the columnar grain diameter. The surface relief accompanying the columnar structure is also a significant factor. Although measurements of d are not available at present, the model appears to explain the observed magnitude as well as the concentration and substrate temperature dependences of perpendicular anisotropy. Measurements are made on the thickness and grain size dependences of perpendicular anisotropy in 81% Ni‐Fe films. The observed results agree qualitatively with predictions based on the present model.