Reorientation Transition in Single-Domain (Ga,Mn)As
  We demonstrate that the interplay of in-plane biaxial and uniaxial anisotropy fields in (Ga,Mn)As results in a magnetization reorientation transition and an anisotropic AC susceptibility which is fully consistent with a simple single domain model. The uniaxial and biaxial anisotropy constants vary respectively as the square and fourth power of the spontaneous magnetization across the whole temperature range up to T_C. The weakening of the anisotropy at the transition may be of technological importance for applications involving thermally-assisted magnetization switching. 
K-Y. Wang, M. Sawicki, K.W. Edmonds, R.P. Campion, S. Maat, C.T.   Foxon, B.L. Gallagher, T. Dietl