In-plane uniaxial anisotropy rotations in (Ga,Mn)As thin films
  We show, by SQUID magnetometry, that in (Ga,Mn)As films the in-plane uniaxial magnetic easy axis is consistently associated with particular crystallographic directions and that it can be rotated from the [-110] direction to the [110] direction by low temperature annealing. We show that this behavior is hole-density-dependent and does not originate from surface anisotropy. The presence of uniaxial anisotropy as well its dependence on the hole-concentration and temperature can be explained in terms of the p-d Zener model of the ferromagnetism assuming a small trigonal distortion. 
M. Sawicki, K-Y. Wang, K. W. Edmonds, R.P. Campion, C.R. Staddon,   N.R.S. Farley, C.T. Foxon, E. Papis, E. Kaminska, A. Pio...