论文标题
分层欧盟的旋转轨道状态和强抗铁磁性
Spin-Orbital States and Strong Antiferromagnetism of Layered Eu$_2$SrFe$_2$O$_6$ and Sr$_3$Fe$_2$O$_4$Cl$_2$
论文作者
论文摘要
绝缘铁化合物欧盟$ _2 $ srfe $ _2 $ o $ _6 $和sr $ _3 $ _3 $ _2 $ _2 $ o $ _4 $ cl $ _2 $具有高温抗Fiferromagnetic（AF）订单，尽管它们具有不同的分层结构。在这里，我们进行了密度的功能计算和蒙特卡洛模拟，以研究其电子结构和磁性特性，并通过分析晶体场，磁各向异性和甲基甲次汇合。我们发现两种化合物都是Mott绝缘子，在高旋转（HS）Fe $^{2+} $状态（$ s $ = 2）以及较弱的水晶场伴随着。尽管它们具有不同的本地协调和晶体场，但Fe $^{2+} $离子具有相同的级别序列和基态配置$（3z^2-r^2）^2（xz，yz，yz）^2（xy）^2（xy）^1（x^2-y^y^2）^1 $。然后，多功能超偏键会产生强大的AF耦合，以及通过自旋轨道耦合（SOC）混合$（3z^2-r^2）/（xz，Yz）$，产生了一个小的平面轨道矩和各向异性。实际上，通过追踪一组不同的自旋轨道状态，我们的密度功能计算证实了两种化合物的强AF耦合和易于平面磁化。此外，使用派生的磁参数，我们的蒙特卡洛模拟给出了néel温度$ t _ {\ rm n} $ = 420 K（372 K）的前者（后者），这很好地繁殖了实验结果。因此，本研究为欧盟提供了统一的图片，$ _2 $ srfe $ _2 $ o $ _6 $和sr $ _3 $ _3 $ fe $ _2 $ o $ _4 $ cl $ cl $ _2 $涉及其电子和磁性。
The insulating iron compounds Eu$_2$SrFe$_2$O$_6$ and Sr$_3$Fe$_2$O$_4$Cl$_2$ have high-temperature antiferromagnetic (AF) order despite their different layered structures. Here we carry out density functional calculations and Monte Carlo simulations to study their electronic structures and magnetic properties aided with analyses of the crystal field, magnetic anisotropy, and superexchange. We find that both compounds are Mott insulators and in the high-spin (HS) Fe$^{2+}$ state ($S$ = 2) accompanied by the weakened crystal field. Although they have different local coordination and crystal fields, the Fe$^{2+}$ ions have the same level sequence and ground-state configuration $(3z^2-r^2)^2(xz,yz)^2(xy)^1(x^2-y^2)^1$. Then, the multiorbital superexchange produces strong AF couplings, and the $(3z^2-r^2)/(xz,yz)$ mixing via the spin-orbit coupling (SOC) yields a small in-plane orbital moment and anisotropy. Indeed, by tracing a set of different spin-orbital states, our density functional calculations confirm the strong AF couplings and the easy planar magnetization for both compounds. Moreover, using the derived magnetic parameters, our Monte Carlo simulations give the Néel temperature $T_{\rm N}$ = 420 K (372 K) for the former (the latter), which well reproduce the experimental results. Therefore, the present study provides a unified picture for Eu$_2$SrFe$_2$O$_6$ and Sr$_3$Fe$_2$O$_4$Cl$_2$ concerning their electronic and magnetic properties.
