论文标题
$ d^3 $ mott绝缘子的单离子各向异性的理论分析
Theoretical analysis of single-ion anisotropy in $d^3$ Mott insulators
论文作者
论文摘要
Mott绝缘子的有效自旋模型由磁性位点，电子填充物及其相互作用之间的对称性确定。这样的自旋汉密尔顿人可以洞悉磁性阶和磁各向异性的机理，超出了海森堡模型。在旋转矩S大于1/2的旋转矩中，原理允许单动各向异性。但是，对于具有较大立方晶体场分裂的$ d^3 $ mott绝缘子，尽管S = 3/2本地矩，但在LS耦合中不存在单离子各向异性。另一方面，已经报道了$ d^3 $材料中的首选磁矩方向，这需要进行进一步的理论研究。在这里，我们使用强耦合扰动理论得出了单离子各向异性相互作用。考虑到LS方案之外的Cubic Crystal场分裂，包括$ E_G $轨道，三角形畸变，Hund的耦合和旋转轨道耦合。对于压缩失真，磁性位点的自旋轨道耦合可以有利于易于轴或易于平面，而阴离子的平面耦合会导致易于轴各向异性。我们将该理论应用于$ \ rm {Crx} _3 $和x = Cl和i，并显示了单离子各向异性对磁性和阴离子位点的自旋轨道耦合强度的依赖性。还讨论了理想二维磁体中单离子各向异性的重要性。
An effective spin model for Mott insulators is determined by the symmetries involved among magnetic sites, electron fillings, and their interactions. Such a spin Hamiltonian offers insight to mechanisms of magnetic orders and magnetic anisotropy beyond the Heisenberg model. For a spin moment S bigger than 1/2, single-ion anisotropy is in principle allowed. However, for $d^3$ Mott insulators with large cubic crystal field splitting, the single-ion anisotropy is absent within the LS coupling, despite S = 3/2 local moment. On the other hand, preferred magnetic moment directions in $d^3$ materials have been reported, which calls for a further theoretical investigation. Here we derive the single-ion anisotropy interaction using the strong-coupling perturbation theory. The cubic crystal field splitting including $e_g$ orbitals, trigonal distortions, Hund's coupling, and spin-orbit coupling beyond the LS scheme are taken into account. For compressed distortion, the spin-orbit coupling at magnetic sites can favor either the easy-axis or the easy-plane while that of anions leads to easy-axis anisotropy. We apply the theory on $\rm{CrX}_3$ with X = Cl and I, and show the dependence of the single-ion anisotropy on the strength of the spin-orbit couplings of both magnetic and anion sites. Significance of the single-ion anisotropy in ideal two-dimensional magnets is also discussed.
