Magnetic circular dichroism of Fe_xCo_1−x alloy single crystal thin films

Soft x‐ray magnetic circular dichroism (SXMCD) of the L2 and L3 edges is used to independently determine magnetic information for single crystal Fe x Co1−x alloythin films (0≤x≤1) grown on ZnSe(001). Similar to surface magneto‐optical Kerr effect (SMOKE) but with element and site specificity, SXMCD, which is the difference between the absorption of left and right circularly polarized soft x rays, can be used to determine a variety of magnetic parameters including spin‐orbit and exchange interaction energies. Measurements made at the National Synchrotron Light Source (NSLS) U4B beamline on the Fe–Co alloy system exhibit unique changes in SXMCD signal as a function of alloy concentration. The SXMCD signal is found to rise linearly with reducing atomic concentration for both the Co and Fe. At the dilute limit of 10% FE (x=0.1), the Fe L3 SXMCD is found to increase by almost a factor of three to near 40%. In some Fe/Co structures, the largest reported SXMCD values in excess of 70% are observed! This example shows the utility of SXMCD in obtaining magnetic information in alloy systems in an element specific and even site specific manner