论文标题
抗铁磁性和抗铁甲状腺可极度有序的平均场研究在四方Cecosi
Mean-field Study of Antiferromagnetic and Antiferroquadrupolar Orderings in Tetragonal CeCoSi
论文作者
论文摘要
我们根据有效局部模型的自洽平均场计算，研究了$ f $ - 电子材料中多极订单的稳定性。该材料在温度压力相图中具有两个有序的阶段：抗铁磁相和非磁相，后者被认为是抗佛罗拉匹配相。同时，抗二甲极线相的起源尚不清楚，因为在地基状态和高度分离的激发态水平之间存在四倍的自由度，而在四方晶体晶体电场（CEF）下，其能量尺度远大于过渡温度。为了了解从顺磁相，抗颈二极相和抗铁磁相的相变序列，当降低温度时，我们检查了有效局部模型中的重要相互作用参数。我们澄清说，抗逆峰性相互作用的$ 3z^2-r^2 $ -Type可以重新构成CEF水平的分裂，即使在没有轨道退化的四方系统中，也可以有助于四极有序。此外，还提供了信息以识别非磁性有序阶段中未知的顺序参数，也提出了磁场中抗拥齿极和抗铁磁状态的稳定性。
We investigate the stability of the multipolar orderings in $f$-electron material CeCoSi based on a self-consistent mean-field calculation for the effective localized model. This material has two ordered phases in the temperature-pressure phase diagram: the antiferromagnetic phase and the nonmagnetic phase, the latter of which has been suggested to be an antiferroquadrupolar phase. Meanwhile, the origin of the antiferroquadrupolar phase has been unclear, since a quadrupole degree of freedom is present only between the ground-state level and highly separated excited-state level under a tetragonal crystalline electric field (CEF), whose energy scale is much larger than the transition temperature. To understand the sequence of the phase transition from the paramagnetic phase, antiferroquadrupolar phase, and antiferromagnetic phase when decreasing the temperature, we examine the important interaction parameters in the effective localized model. We clarify that the $3z^2-r^2$-type of the antiferroquadrupolar interactions can renormalize the CEF level splitting, which assists a quadrupolar ordering even in a tetragonal system without orbital degeneracy. Moreover, the stability of the antiferroquadrupolar and antiferromagnetic states in a magnetic field and the behavior of the magnetic/quadrupolar susceptibility are also presented for the information to identify the unknown order parameter in the nonmagnetic ordered phase.
