Enhancement of the Co magnetic moment in bcc Co1-xMnx on MgO

Using X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (MCD), we show that the elemental Co moment for MBE grown thin films of bcc Co1_-xMn_x grown on MgO(001) is enhanced by 40% to a maximum value of 2.1 μ_B at x =0.24. The net Mn moment is found to align parallel with Co for all concentrations and remains roughly constant until x =0.3, then drops steadily, up to x =0.7, where the total moment of the film abruptly collapses to zero. Using a low-concentration Mn moment of 3.0 μ_B, the average magnetization lies directly on the Slater-Pauling (SP) curve for concentrations up to about x =.25, where it reaches a maximum moment of 2.3 μ_B /atom. This peak is slightly shifted and the slope is steeper on the high-Mn concentration side of the peak relative to the standard SP curve. This is in stark contrast to the fcc CoMn and hcp CoCr bulk behavior which shows only a rapid total moment reduction with Mn concentration.

This material is based upon work supported by the National Science Foundation under Grant ECCS-1542210. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Con.