Magnetic circular dichroism in X-ray fluorescence of Heuseler alloys at threshold excitation

The results of fluorescence measurements of magnetic circular dichroism (MCD) in Mn L 2,3 X-ray emission and absorption for Heusler alloys NiMnSb and Co 2 MnSb are presented. Very intense resonance Mn L 3 emission is found at the Mn 2p 3/2 threshold and attributed to a peculiarity of the threshold excitation in materials with a half-metallic character of the electronic structure. The excitation energy dependence of Mn L 2,3 X-ray emission spectra (XES) was measured at beamline ID12B at the European Synchrotron Radiation Facility (ESRF, Grenoble) using 83% circularly polarized X-rays. A very large MCD effect found in XES is attributed to strong exchange splitting of spin-up and spin-down Mn 3d states. The anomalously high ratio of L 2 emission intensity to L 3 emission intensity is found.