Magnetic Phase Transitions to an Incommensurate Structure in LiMn2O4 Compound

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.