  We demonstrate sensitivity of the Mn 3d valence states to strain in the
ferromagnetic semiconductors (Ga,Mn)As and (Al,Ga,Mn)As, using x-ray magnetic
circular dichroism (XMCD). The spectral shape of the Mn $L_{2,3}$ XMCD is
dependent on the orientation of the magnetization, and features with cubic and
uniaxial dependence are distinguished. Reversing the strain reverses the sign
of the uniaxial anisotropy of the Mn $L_3$ pre-peak which is ascribed to
transitions from the Mn 2p core level to p-d hybridized valence band hole
states. With increasing carrier localization, the $L_3$ pre-peak intensity
increases, indicating an increasing 3d character of the hybridized holes.
