Magnetic circular dichroism of x-ray absorption spectroscopy at rare-earth L2,3 edges in RE2Fe14B compounds (RE = La, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu)

摘要

Magnetic circular dichroism (MCD) in the x-ray absorption spectroscopy (XAS)at the L2,3 edges for almost entire series of rare-earth (RE) elements inRE2Fe14B, is studied experimentally and theoretically. By a quantitativecomparison of the complicated MCD spectral shapes, we find that (i) the 4f-5dintra-atomic exchange interaction not only induces the spin and orbitalpolarization of the 5d states, which is vital for the MCD spectra of theelectric dipole transition from the 2p core states to the empty 5d conductionband, but also it accompanies a contraction of the radial part of the 5d wavefunction depending on its spin and orbital state, which results in theenhancement of the 2p-5d dipole matrix element, (ii) there are cases where thespin polarization of the 5d states due to the hybridization with the spinpolarized 3d states of surrounding irons plays important roles, and (iii) theelectric quadrupole transition from the 2p core states to the magnetic vale!nce 4f states is appreciable at the pre-edge region of the dipole spectrum.Especially, our results evidence that it is important to include theenhancement effect of the dipole matrix element in the correct interpretationof the MCD spectra at the RE L2,3 edges.