X-ray magnetic circular dichroism at the Gd L edges in Gd-Ni-Co amorphous systems

Abstract

X-ray magnetic circular dichroism (XMCD) experiments have been performed at the ${\mathrm{L}}_{2,3}$ edges of gadolinium in the amorphous Gd-Ni-Co and Gd-Ni alloys in order to observe the effect of the transition metal on the polarization of the rare-earth 5d band. The magnetic properties of the Gd-Ni-Co alloys, weak anisotropy or perpendicular easy axis of magnetization, are very well suited to XMCD experiments and very large XMCD signals are observed at the Gd ${\mathrm{L}}_{2,3}$ edges. The signals corrected from the circular polarization rate (${\mathrm{P}}_{\mathrm{c}}$ =0.65) can reach up to -22% at the ${\mathrm{L}}_{2}$ and +11% at the ${\mathrm{L}}_{3}$ for some samples. The V-like behavior of the XMCD signal at the Gd L edges near the compensation temperature is understood in terms of distribution of the Co concentration in the Gd-Ni-Co sputtered films. Within the spin-dependent radial matrix model, the evolution of the XMCD intensity in the Gd-Ni-Co films as a function of the Co concentration qualitatively accounts for the variation of the spin-dependent final-state density \ensuremath{\Delta}\ensuremath{\rho}/\ensuremath{\rho} monitored by the Co concentration.