Abstract

Possible second-order magnetic phase transitions to the incommensurate magnetic structure in the orthorhombic phase of LiMn₂O₄ compound have been investigated. It is shown that “weak Lifshitz condition” holds for this compound (i.e., Lifshits invariants are immaterial in all transitions being considered), and only the incommensurate phase, in which the wavevector near the transition point varies continuously with temperature and pressure, can be formed. A transition is considered both in the exchange approximation occurring in three irreducible representations forming an exchange multiplet as well as in one and two irreducible representations. Expressions have been derived for the mean density of the magnetic moment emerging because of such transitions. It is found that structures of the types of a longitudinal spin wave, a transverse spin wave with polarization along the crystallographic axes perpendicular to the wavevector of the structure, as well as certain superpositions of these waves can be formed in the system.

中文翻译：

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LiMn 2 O 4化合物中的磁相转变为不对称结构

摘要

LiMn ₂ O ₄的正交晶相中可能的二阶磁性相转变为不等价的磁性结构化合物已经过调查。结果表明，该化合物具有“弱Lifshitz条件”（即，考虑到所有Lifshits不变量，所有过渡都无关紧要），并且只有不相称的相位（其中，过渡点附近的波矢随温度和压力而连续变化）才可以。形成。在形成交换多重的三个不可约表示中以及在一个和两个不可约表示中发生的交换逼近中均考虑了跃迁。由于这种转变，已经得出了出现的磁矩的平均密度的表达式。已发现，结构类型为纵向自旋波，横向自旋波，其沿垂直于结构波矢量的结晶轴极化，