Magnetic anisotropy switching in(Ga,Mn)Aswith increasing hole concentration

Abstract

We study a possible mechanism of the switching of the magnetic easy axis as a function of hole concentration in $(\mathrm{Ga},\mathrm{Mn})\mathrm{As}$ epilayers. In-plane uniaxial magnetic anisotropy along [110] is found to exceed intrinsic cubic magnetocrystalline anisotropy above a hole concentration of $p=1.5\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ at $4\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. This anisotropy switching can be realized by postgrowth 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) and 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.