MnAs/GaAs（100）薄膜的磁晶各向异性和单轴性
Magnetocrystalline anisotropy and uniaxiality of MnAs/GaAs(100) films
摘要：
本文研究了GaAs（100）衬底上外延生长的MnAs薄膜的磁性。我们解决的磁矩，铁磁转变温度（$T_c$）和磁晶各向异性常数对外延条件的依赖性。从彻底的结构和磁性的调查，我们的研究结果表明，在MnAs薄膜的应变和磁性能之间的关系比一个简单的拉伸/压缩的晶胞轴更复杂。虽然各向异性常数略有增加，但饱和时磁矩的增强是显著的。X-射线磁性圆二色性结果表明自旋和轨道矩的行为与$T_c$的结构转变一致。特别是，我们发现，轨道自旋矩的比例显示出显着增加的铁磁$α$ -和顺磁$β$ -相的共存区域，结果是很好地符合所观察到的增加的$c/a$ -比在相同的温度区域。的\textit{ab initio}密度泛函计算表明，磁性能是更敏感的面内轴的变化相比，面外轴的变化，这是解释的能带结构的分析。用\textit{ab initio}动力学平均场论计算了MnAs中的电子关联效应。
英文摘要：
We present an investigation of the magnetic behavior of epitaxial MnAs films grown on GaAs(100). We address the dependence of the magnetic moment, ferromagnetic transition temperature ($T_c$) and magnetocrystalline anisotropy constants on epitaxial conditions. From thorough structural and magnetic investigations, our findings indicate a more complex relationship between strain and magnetic properties in MnAs films than a simple stretch/compression of the unit cell axes. While a small increase is seen in the anisotropy constants the enhancement of the magnetic moment at saturation is significant. X-ray magnetic circular dichroism results show a behavior of the spin- and orbital-moment which is consistent with a structural transition at $T_c$. In particular, we find that the ratio of the orbital to spin moment shows a marked increase in the coexistence region of the ferromagnetic $α$- and paramagnetic $β$-phases, a result that is well in accord with the observed increase of the $c/a$-ratio in the same temperature region. The \textit{ab initio} density functional calculations reveal that the magnetic properties are more sensitive towards change in in-plane axis as compared to a change of the out-of-plane axis, which is explained by the analysis of band structures. The effects of electron correlation in MnAs using \textit{ab initio} dynamical mean field theory are also presented.
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