The problem of choosing of the group of symmetries of paramagnetic phase in the theory of magnetic phase transitions and the exchange multiplets

TL;DR

This paper discusses the appropriate symmetry group for modeling magnetic phase transitions in transition metal magnetics, emphasizing the use of the exchange group GxO(3) within Landau theory to describe various magnetic phases.

Contribution

It introduces the exchange group GxO(3) as the symmetry group for paramagnetic phases, enabling comprehensive description of magnetic and spin-orbit phase transitions.

Findings

Exchange group GxO(3) is suitable for describing paramagnetic phases.

The exchange multiplet models spin-orbit phase transitions.

The approach unifies magnetic and structural phase transition descriptions.

Abstract

It is shown that for the theoretical description of the magnetic and structural phase transitions in the magnetics with magnetoactive ions of transition metals within the framework of the Landau theory of phase transitions the exchange group GxO(3) should be chosen as the group of symmetry of paramagnetic phase. Such a choice allows to describe the transition from the paramagnetic phase into the isotropic magnetically ordered phase (at Tc), and the spin-orbit transition from the isotropic into the anisotropic phase (at T<Tc). The exchange multiplet describes the spin-orbit phase transition.