First-principles study of the origin and nature of ferromagnetism in Ga 1-x Mn x As
First-principles study of the origin and nature of ferromagnetism in Ga 1-x Mn x As
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DOI：
10.1103/physrevb.63.165206
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发表时间：
2000-11
影响因子：
3.7
通讯作者：
S. Sanvito;P. Ordejón;N. A. Hill
中科院分区：
文献类型：
--
作者：
S. Sanvito;P. Ordejón;N. A. Hill
在密度泛函理论的局域自旋密度近似下，对较宽的Mn浓度范围内的稀释${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$的性质进行了计算。M“ulliken布居分析和轨道分辨态密度分析表明，在GaAs中，Mn的组态与{3d}^{5}或${3d}^{6}相容；然而，由于Mnd态与GaAs价带之间存在较大的p-d杂化，占据不是整数。GaAs导带的自旋分裂随Mn离子浓度的变化呈类平均场的线性变化，表现出与Mn离子的铁磁耦合。相反，价带与锰杂质是反铁磁耦合的，自旋分裂不是线性依赖于锰的浓度。这表明平均场近似在掺锰的砷化镓中被打破，必须考虑多次散射的修正。我们在一个简单的自由电子模型中计算了这些修正，如果假定交换常数$(N\ensuremath{\beta}=\ensuremath{-}4.5\mathrm{eV})$较大，则与从头计算结果符合得很好。
The properties of diluted ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ are calculated for a wide range of Mn concentrations within the local-spin-density approximation of density-functional theory. M\"ulliken population analyses and orbital-resolved densities of states show that the configuration of Mn in GaAs is compatible with either ${3d}^{5}$ or ${3d}^{6};$ however, the occupation is not integer due to the large p-d hybridization between the Mn d states and the valence band of GaAs. The spin splitting of the conduction band of GaAs has a mean-field-like linear variation with the Mn concentration, and indicates ferromagnetic coupling with the Mn ions. In contrast, the valence band is antiferromagnetically coupled with the Mn impurities, and the spin splitting is not linearly dependent on the Mn concentration. This suggests that the mean-field approximation breaks down in the case of Mn-doped GaAs, and corrections due to multiple scattering must be considered. We calculate these corrections within a simple free-electron model, and find good agreement with our ab initio results if a large exchange constant $(N\ensuremath{\beta}=\ensuremath{-}4.5\mathrm{eV})$ is assumed.