Universal low-temperature tricritical point in metallic ferromagnets and ferrimagnets

TL;DR

This paper generalizes a theory of quantum phase transitions in metallic ferromagnets, showing that fluctuation-induced first-order transitions occur across various magnetic classes and materials, including ferrimagnets and anisotropic ferromagnets.

Contribution

It extends the existing theory to encompass different magnetic symmetries and ferrimagnets, broadening the understanding of low-temperature first-order transitions in metallic magnets.

Findings

First-order transition mechanism applies across magnetic classes.

Explains first-order transitions in anisotropic ferromagnets like UGe2.

Expands the class of materials exhibiting low-temperature first-order transitions.

Abstract

An earlier theory of the quantum phase transition in metallic ferromagnets is revisited and generalized in three ways. It is shown that the mechanism that leads to a fluctuation-induced first-order transition in metallic ferromagnets with a low Curie temperature is valid, (1) irrespective of whether the magnetic moments are supplied by the conduction electrons or by electrons in another band, (2) for ferromagnets in the XY and Ising universality classes as well as for Heisenberg ferromagnets, and (3) for ferrimagnets as well as for ferromagnets. This vastly expands the class of materials for which a first-order transition at low temperatures is expected, and it explains why strongly anisotropic ferromagnets, such as UGe2, display a first-order transition as well as Heisenberg magnets.