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Oxygen-octahedral distortion and electronic correlation induced semiconductor gaps in ferrimagnetic double perovskite Ca2MReO6 (M = Cr, Fe)

机译：氧气 - 八面体畸变和电子相关诱导的含铁纤维双钙钛矿CA2MREO6（M = Cr，Fe）中的半导体间隙

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摘要

Motivated by experimental nonmetallic features and high magnetic Curie temperatures of 360 and 522 K in double perovskite Ca2CrReO6 and Ca2FeReO6, we systematically investigate the structural, electronic, and magnetic properties of Ca2MReO6 (M = Cr, Fe) by combining the modified Becke-Johnson (mBJ) exchange potential with usual generalized gradient approximation (GGA). Our full optimization leads to stable ground-state structures with monoclinic symmetry (P2(1)/n) consistent with experiment. The mBJ calculation successfully produces ferrimagnetic phase with semiconductor gaps of 0.38 eV and 0.05 eV, respectively, in contrast with wrong metallic phases from GGA calculations. With the spin-orbit coupling (SOC) taken into account, the Ca2MReO6 (M = Cr, Fe) shows high magneto-crystalline anisotropy (MCA) with the magnetic easy axis along the [010] direction. Although reducing to 0.31 and 0.03 eV, the semiconductor gaps remain open in spite of the SOC broadening of the Re t(2g) bands. Therefore, our DFT investigation has established the correct ferrimagnetic semiconductor ground states for the double perovskite Ca2MReO6 (M = Cr, Fe) materials. Our analysis shows that the semiconductor gaps are due to orbital-selective splitting on Re t(2g) bands in the minority-spin channel, originated from the O-octahedral distortion and Coulomb correlation effect. This mechanism, different from that in other double perovskite materials such as Sr2CrOsO6, Ca2CrOsO6 and Sr2FeOsO6, can be useful to fully understand chemical and physical properties of double perovskite compounds.
机译：通过实验性的非金属特征和360和522 k的高磁性居里温度，通过组合改性的Becke-Johnson（Pro）来系统地研究CA2MREO6（M = CR，FE）的结构，电子和磁性，通过组合（ MBJ）与通常的广义梯度近似（GGA）的交换电位。我们的全部优化导致稳定的地态结构具有单斜视对称性（P2（1）/ n）与实验一致。 MBJ计算成功地产生了与0.38eV的半导体间隙和0.05eV的亚铁磁相，与来自GGA计算的错误金属相。考虑到旋转轨道耦合（SOC），Ca2mreo6（m = Cr，Fe）显示了沿[010]方向的高磁体晶体各向异性（MCA），磁性易轴。尽管降低到0.31和0.03eV，但是，尽管Re T（2G）带扩展了SoC扩大，但半导体间隙保持开放。因此，我们的DFT调查已经为双钙钛矿CA2MREO6（M = Cr，Fe）材料建立了正确的铁磁半导体地面状态。我们的分析表明，半导体间隙是由于少数旋转通道中的RE T（2G）带上的轨道选择性分裂，源自O-OCTAHEDRAL失真和库仑相关效果。这种机制与其他双钙钛矿材料如SR2CROSO6，CA2CROSO6和SR2FEOSO6不同，可用于完全理解双钙钛矿化合物的化学和物理性质。

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  • 来源
    《RSC Advances》 |2015年第78期|共10页
  • 作者

    Gong Sai; Guo San-Dong; Chen Peng; Liu Bang-Gui;

  • 作者单位

    Chinese Acad Sci Inst Phys Beijing Natl Lab Condensed Matter Phys Beijing 100190 Peoples R China;

    Chinese Acad Sci Inst Phys Beijing Natl Lab Condensed Matter Phys Beijing 100190 Peoples R China;

    Chinese Acad Sci Inst Phys Beijing Natl Lab Condensed Matter Phys Beijing 100190 Peoples R China;

    Chinese Acad Sci Inst Phys Beijing Natl Lab Condensed Matter Phys Beijing 100190 Peoples R China;

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  • 正文语种 eng
  • 中图分类 化学;
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