  The magneto-crystalline anisotropy (MCA) of (Ga,Mn)As films has been studied
on the basis of ab-initio electronic structure theory by performing magnetic
torque calculations. An appreciable contribution to the in-plane uniaxial
anisotropy can be attributed to an extended region adjacent to the surface.
Calculations of the exchange tensor allow to ascribe a significant part to the
MCA to the exchange anisotropy, caused either by a tetragonal distortion of the
lattice or by the presence of the surface or interface.
