Local lattice distortions around $\rm{Mn^{2+}}$ cause in-plane uniaxial   magnetic anisotropy in Ga(Mn)As
  We theoretically investigate the interplay between local lattice distortions around $\rm{Mn^{2+}}$ ion impurity and the ion's magnetic polarization, mediated through spin-orbit coupling of hole. We show that the tetrahedral symmetry around $\rm{Mn^{2+}}$ ion impurity is spontaneously broken even in the paramagnetic regime. Modest local lattice distortions around the impurity $\rm{Mn^{2+}}$ ion, along with the growth strain, stabilize magnetization along $< 110 >$ directions, in the ferromagnetic regime. We explain the experimentally observed in-plane uniaxial magnetic anisotropy seen in this system using this symmetry-breaking mechanism. 
Hemachander Subramanian, J. E. Han
cond-mat.mtrl-sci