  Using x-ray magnetic circular dichroism (XMCD), we determine the
element-specific character and polarization of unoccupied states near the Fermi
level in (Ga,Mn)As and (In,Ga,Mn)As thin films. The XMCD at the As K absorption
edge consists of a single peak located on the low-energy side of the edge,
which increases with the concentration of ferromagnetic Mn moments. The XMCD at
the Mn K edge is more detailed and is strongly concentration-dependent, which
is interpreted as a signature of hole localization for low Mn doping. The
results indicate a markedly different character of the polarized holes in
low-doped insulating and high-doped metallic films, with a transfer of the hole
orbital magnetic moment from Mn to As sites on crossing the metal-insulator
transition.
