Evidence for selective resputtering as the growth mechanism of pair-order anisotropy in amorphous TbFe films

Abstract

Processing conditions for rf magnetron sputter-deposited amorphous TbFe films in which an atomic scale structural anisotropy (ASSA) results as a natural consequence of selective resputtering at the film surface during growth are presented. The ASSA, measured using polarization-dependent X-ray absorption fine structure with quantitative modelling via a parametrized nonlinear least squares fitting, is described as a pair order anisotropy (POA) where a statistical preference exists for like atom pairs in-plane and unlike atom pairs perpendicular to the film plane. The perpendicular magnetic anisotropy (PMA) energy increases with increasing POA for samples grown using decreasing rf power and increasing working gas pressure. The POA directly reflects the anisotropic electrostatic environment at the rare earth site which is required for PMA to result from a single ion anisotropy mechanism.