Structural stability and half-metallicity of the zinc-blende phase of Al1-xCrxAs: Density-functional study
Structural stability and half-metallicity of the zinc-blende phase of Al1-xCrxAs: Density-functional study
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DOI：
10.1103/physrevb.80.224417
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发表时间：
2009-12
影响因子：
3.7
通讯作者：
Yong-Hong Zhao;Guo-Ping Zhao;Y. Liu;Banggui Liu
中科院分区：
文献类型：
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作者：
Yong-Hong Zhao;Guo-Ping Zhao;Y. Liu;Banggui Liu
用精确的全电位线性增广平面波法研究了闪锌矿相Al1-xCrxAs铁磁半导体合金的结构稳定性和半金属铁磁性。通过比较各种结构的总能量，证实了闪锌矿相相对于NiAs相的相对稳定性以及铁磁性相对于反铁磁性的相对稳定性。对所有这些结构进行了充分的优化，包括晶胞体积、四面体晶胞的c/a和内部参数。我们的计算表明，当铬含量低于30%时，闪锌矿相更稳定，而NiAs相在铬含量较高时更稳定。因此，当x小于0.3时，可以得到闪锌矿结构的Al1-xCrxAs块体，而当x较大时，只有外延膜存在。对于x在0.125~1.0%范围内的所有这些化合物，闪锌矿中都有很强的半金属铁磁性。此外，还考虑了自旋-轨道相互作用的影响，给出了包括自旋贡献和轨道贡献在内的总磁矩。自旋-轨道相互作用通过将多数自旋态反射到少数自旋能隙中，破坏了理想的半金属铁磁性，然而，在所有替代情况下，自旋极化的降低仅为0.2%左右。最后给出了平均场近似下的交换参数和居里温度。我们对Al1-xCrxAs的系统计算对于阐明Al1-xCrxAs中的半金属铁磁性和探索未来信息技术中基于Al1-xCrxAs的高性能自旋电子器件是有用的。
An accurate full-potential linear augmented plane waves method has been used to investigate the structural stability, half-metallic ferromagnetism of the zinc-blende phase of the ferromagnetic semiconductor alloy Al1-xCrxAs. The relative stability of the zinc-blende phase with respect to the NiAs one and the ferromagnetism to the antiferromagnetism are confirmed by comparing total energy of various structures. Full optimization for all these structures is performed, including the cell volume, c/a for tetrahedral cells and internal parameters. Our calculation shows that when the Cr composition is less than 30%, the zinc-blende phase is more stable, whereas the NiAs one is more stable for more Cr composition. Therefore, bulk Al1-xCrxAs with zinc-blende structure can be obtained when x is smaller than 0.3, whereas only epitaxial films can exist for larger x. For all these compounds with x ranging from 0.125 to 1.0, robust half-metallic ferromagnetism is found in the zinc-blende phase. In addition, the effects of the spin-orbital interaction are considered and the total magnetic moments including both the spin and orbital contributions are presented. The spin-orbital interaction will destroy the perfect half-metallic ferromagnetism by reflecting some majority-spin states into the minority-spin gap, however, the decrease of the spin-polarization is only about 0.2% for all substitutional cases. At last, we give the exchange parameters and consecutively the Curie temperature within the mean-field approximation. Our systematical calculation for Al1-xCrxAs is useful to elucidate the half-metallic ferromagnetism in Al1-xCrxAs and to explore high-performance spintronic devices based on Al1-xCrxAs in future information technologies.