Anisotropic X-ray magnetic linear dichroism

Abstract

In this Chapter, the reader will be able to gain a deeper understanding in the angular dependence of x-ray absorption (XA) and x-ray magnetic linear dichroism (XMLD). The scattering tensor provides a general framework for the XA intensity, which is a function of the relative orientation of the magnetization M, the x-ray polarization E and the crystalline axes. In cubic crystal field, the XMLD is a linear combination of two independent spectra, which means that the maximum of the XMLD will be photon energy dependent and no longer at E ∥ M. The angular dependence of the XMLD can be separated into an isotropic part, which rotates with M, and an anisotropic part, which depends on the orientation of the crystal axes. At the Ni2+ L2 edge, where the isotropic part vanishes, the angular dependence is fully determined by the anisotropic part, which obtains maximal intensity when E and M have equal but opposite angles with respect to the [100] direction. In the past this complication has not been appreciated, leading in confusion and misinterpretation in the literature.