Anisotropy of theL2,3x-ray magnetic linear dichroism of Fe films on GaAs: Experiment andab initiotheory

Abstract

We report investigations of the anisotropy of the x-ray magnetic linear dichroism (XMLD) of thin single-crystalline Fe films on GaAs substrates with film thicknesses of 3 nm and 7 nm, respectively. The orientation of the in-plane Fe magnetization with respect to the crystal axes is stepwise rotated from the [1 1 0] to the [0 1 0] direction and the $\text{Fe}\text{ }{L}_{2,3}$ XMLD spectrum is measured at every orientation step. A highly anisotropic XMLD signal at the $\text{Fe}\text{ }{L}_{2}$ and ${L}_{3}$ edges is observed, which origin is analyzed in detail. We show that the measured anisotropic XMLD spectra are in reasonable agreement with ab initio calculated spectra. The XMLD anisotropy is shown to be a consequence of the cubic crystal-field split density of $3d$ states, which are selectively probed by transitions from the spin-orbit and exchange-split $2p$ core levels. We furthermore investigate computationally the influences of the spin-orbit interaction of the $\text{Fe}\text{ }3d$ valence electrons as well as of stress in the Fe films. The $\text{Fe}\text{ }3d$ spin-orbit interaction only leads to small modifications of the XMLD spectra, whereas tetragonal deformation of the films can cause a larger modification of the spectra.