RH 4D SPIN POLARIZATION OF VALENCE STATES IN CO-RH

X-ray fluorescence spectra involving Rh valence states in Co-Rh-based alloys have been recorded using circularly polarized photons from the Hellos II helical undulator at ESRF. Magnetic circular dichroism in th e x-ray emission (XEMCD) is observed. To help identify the significanc e of the XEMCD signal, spin-polarized density functional electronic st ructure calculations for Co3Rh have been performed using the general p otential linearized augmented plane wave method and appropriate transi tion matrix elements included to calculate spin-polarized spectra. The theoretical spin polarization is in excellent agreement with experime nt inso far as both reveal that, at rhodium sites, polarization is con centrated close to the Fermi edge. The width of the peak in spin polar ization can be varied by substituting Ru or Pd for Ph. The size of the change is discussed in relation to the measured magnetization and int erpreted with the help of a generalized Slater-Pauling approach [A. R. Williams et al., IEEE Trans. Magn. MAG-19, 1983 (1983)].