We study a possible mechanism of the switching of the magnetic easy axis as a function of hole concentration in (Ga,Mn)As epilayers. In-plane uniaxial magnetic anisotropy along [110] is found to exceed intrinsic cubic magnetocrystalline anisotropy above a hole concentration of p = 1.5 * 10^21 cm^-3 at 4 K. This anisotropy switching can also be realized by post-growth annealing, and the temperature-dependent ac susceptibility is significantly changed with increasing annealing time. On the basis of our recent scenario [Phys. Rev. Lett. 94, 147203 (2005); Phys. Rev. B 73, 155204 (2006).], we deduce that the growth of highly hole-concentrated cluster regions with [110] uniaxial anisotropy is likely the predominant cause of the enhancement in [110] uniaxial anisotropy at the high hole concentration regime. We can clearly rule out anisotropic lattice strain as a possible origin of the switching of the magnetic anisotropy.
@article{arxiv.cond-mat/0601603,
title = {Magnetic anisotropy switching in (Ga,Mn)As with increasing hole concentration},
author = {K. Hamaya and T. Watanabe and T. Taniyama and A. Oiwa and Y. Kitamoto and Y. Yamazaki},
journal= {arXiv preprint arXiv:cond-mat/0601603},
year = {2009}
}