Magnetic dichroism at Tb L_2,3-edges in Fe-Tb and Co-Tb amorphous thin films

In order to investigate the magnetic structures of the Fe-Tb and the Co-Tb amorphous alloy systems, we have measured the composition dependence of magnetic circular dichroism (MCD) spectra at the Tb L_2,3-edges. The MCD measurements show that the majority spin direction of the 5d_3/2(5d_5/2)-projected electrons is parallel (anti-parallel) to the total moment in Tb-poor alloys, but anti-parallel (parallel) in Tb-rich alloy. The significant difference in the MCD intensities between the Fe-Tb and the Co-Tb alloy systems is thought to be associated with the difference in the populations of the conduction electrons between the two alloy systems.