Competition between cubic and uniaxial anisotropy inGa1−xMnxAsin the low-Mn-concentration limit

Abstract

We have studied the dependence of the cubic and uniaxial magnetic anisotropy terms in ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ on temperature $T$ and hole concentration $p$. For the purpose of this study we prepared a series of ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ layers with low Mn concentration $(x\ensuremath{\approx}0.01)$, codoped by Be in the range $3.0\ifmmode\times\else\texttimes\fi{}{10}^{19}lpl8.5\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$, and grown on hybrid $\mathrm{Zn}\mathrm{Se}∕\mathrm{Ga}\mathrm{As}$ substrates. The use of such hybrid substrates was intended to obtain ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ layers in which\char22{}due to the small lattice mismatch between ${\mathrm{Ga}}_{0.99}{\mathrm{Mn}}_{0.01}\mathrm{As}$ and ZnSe\char22{}the uniaxial and the cubic anisotropy terms are comparable, so that the contributions of both types of anisotropy could be investigated. The effects of magnetic anisotropy were studied by polar magneto-optical Kerr effect, which allowed us to monitor the reversal process of perpendicular magnetization. The results showed that cubic anisotropy is highly sensitive to both $p$ and $T$. Specifically, we have found that in samples with high $p$ the cubic anisotropy term is dominant at low $T$, but decreases rapidly as $T$ increases. In sharp contrast, uniaxial anisotropy shows only a weak dependence on $p$ and $T$, thus dominating at temperatures close to ${T}_{C}$ even in samples with high $p$. These results show that magnetic anisotropy and the magnetization reversal process in ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ can be engineered by an appropriate choice of the temperature and carrier concentration.