Crystal field effect on X-ray magnetic circular dichroism spectra at the L2,3 absorption edges of mixed-valence Ce and Yb compounds in high magnetic fields

Abstract

A theoretical study is presented, with an extended single impurity Anderson model, for the crystal field effect on the X-ray magnetic circular dichroism (XMCD) spectra at L2,3 edges of mixed-valence Ce and Yb compounds in high magnetic fields. The crystal field acting on the 4f electrons is assumed to have cubic symmetry. Due to the competition among the effects of crystal field, mixed valency, and external magnetic field, the magnetic-field-dependence of XMCD spectra exhibits a variety of features; for instance, the branching ratio, R(L2/L3), of L2 and L3 XMCD intensities of Ce compounds can take R(L2/L3) > 1.0 and 0 and <0. It is shown that the magnetic-field-dependence of the total XMCD intensity I(L2 + L3) is proportional to the magnetization curve, but that of R(L2/L3) gives more precise information on the ground state wavefunction in magnetic fields. A new and useful method to correlate the XMCD spectra, the 4f magnetization and the ground state wavefunction is proposed and used to discuss the relation between I(L2 + L3) and the magnetization curve and that between R(L2/L3) and the ground state wavefunction.