Sr $_{2}$ CrMoO $_{6}$的磁性：从头算和模型研究
Magnetism in Sr$_{2}$CrMoO$_{6}$: A combined abinitio and model study
摘要：
使用第一性原理密度泛函理论（DFT）的计算和精确的对角化研究的第一性原理推导的模型相结合，我们进行了微观分析的半金属双钙钛矿化合物，Sr $_2$ CrMoO $_6$，一个姐妹化合物的备受讨论的材料Sr $_2$ FeMoO $_6$的磁性。Sr $_2$ CrMoO $_6$的电子结构虽然乍一看与Sr $_2$ FeMoO $_6$相似，但仔细观察后发现与Sr $_2$ FeMoO $_6$的电子结构有很大差异.在这种情况下，我们的研究突出了两个过渡金属位点之间的电荷转移能量的重要性。与Sr $_2$ FeMoO $_6$中的Fe $d$相比，由于Sr $_2$ CrMoO $_6$中的Cr $d$态的移位引起的电荷转移能量的变化抑制了Cr $t_{2g}$和Mo $t_{2g}$之间的杂化。这大大削弱了讨论的Sr $_2$ FeMoO $_6$的杂化驱动的磁性机制。我们的研究表明，尽管如此，Sr $_2$ CrMoO $_6$的磁转变温度仍然很高，因为额外的超交换贡献的磁性出现与有限的内禀矩在Mo网站上开发。我们进一步讨论的情况相比，另一个相关的双钙钛矿化合物，Sr $_2$ CrWO $_6$。我们还研究了超越DFT的相关性的影响，使用动态平均场论（DMFT）。
英文摘要：
Using a combination of first-principles density functional theory (DFT) calculations and exact diagonalization studies of a first-principles derived model, we carry out a microscopic analysis of the magnetic properties of the half-metallic double perovskite compound, Sr$_2$CrMoO$_6$, a sister compound of the much discussed material Sr$_2$FeMoO$_6$. The electronic structure of Sr$_2$CrMoO$_6$, though appears similar to Sr$_2$FeMoO$_6$ at first glance, shows non trivial differences with that of Sr$_2$FeMoO$_6$ on closer examination. In this context, our study highlights the importance of charge transfer energy between the two transition metal sites. The change in charge transfer energy due to shift of Cr $d$ states in Sr$_2$CrMoO$_6$ compared to Fe $d$ in Sr$_2$FeMoO$_6$ suppresses the hybridization between Cr $t_{2g}$ and Mo $t_{2g}$. This strongly weakens the hybridization-driven mechanism of magnetism discussed for Sr$_2$FeMoO$_6$. Our study reveals that, nonetheless, the magnetic transition temperature of Sr$_2$CrMoO$_6$ remains high since additional superexchange contribution to magnetism arises with a finite intrinsic moment developed at the Mo site. We further discuss the situation in comparison to another related double perovskite compound, Sr$_2$CrWO$_6$. We also examine the effect of correlation beyond DFT, using dynamical mean field theory (DMFT).
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