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

TL;DR

This study investigates how increasing hole concentration in (Ga,Mn)As epilayers causes a switch in magnetic easy axis, highlighting the role of hole-rich clusters and ruling out lattice strain as the cause.

Contribution

It demonstrates that high hole concentration induces magnetic anisotropy switching via cluster growth, providing insights into magnetic behavior control in (Ga,Mn)As.

Findings

In-plane uniaxial anisotropy exceeds cubic anisotropy above p=1.5x10^21 cm^-3.

Annealing enhances uniaxial anisotropy and alters ac susceptibility.

Cluster growth with [110] anisotropy likely causes the anisotropy switching.

Abstract

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.