Valence band orbital polarization in III-V ferromagnetic semiconductors
  The element-specific technique of x-ray magnetic circular dichroism (XMCD) is used to directly determine the magnitude and character of the valence band orbital magnetic moments in (III,Mn)As ferromagnetic semiconductors. A distinct dichroism is observed at the As K absorption edge, yielding an As 4p orbital magnetic moment of around -0.1 Bohr magnetons per valence band hole. This is strongly influenced by strain, indicating its crucial influence on the magnetic anisotropy. The dichroism at the Ga K edge is much weaker. The K edge XMCD signals for Mn and As both have positive sign, which indicates the important contribution of Mn 4p states to the Mn K edge spectra. 
A.A. Freeman, K.W. Edmonds, G. van der Laan, R.P. Campion, N.R.S.   Farley, A.W. Rushforth, T.K. Johal, C.T. Foxon, B.L. Gal...