Unconventional Magnetism: Symmetry Classification, Hybrid-parity and Unconstrained-parity Classes

TL;DR

This paper introduces a comprehensive symmetry classification for unconventional magnetism, predicting new classes of spin textures and demonstrating their potential for spintronic applications through first-principles calculations.

Contribution

It systematically classifies unconventional magnetism based on symmetry and parity, predicting hybrid-parity and unconstrained-parity classes, and explores their spintronic functionalities.

Findings

Predicted two new classes: hybrid-parity and unconstrained-parity magnets.

Derived symmetry criteria for categorizing hybrid-parity magnets.

Demonstrated coexistence of spin current and Edelstein effects in FePO4.

Abstract

Unconventional magnetism has emerged as a transformative frontier in condensed matter physics. Such phases are characterized by substantial non-relativistic spin splitting (NSS) in symmetry-compensated magnets. They have been classified by the parity of their spin textures under momentum inversion, leading to the paradigms of altermagnets (even-parity) and odd-parity magnets. However, the full symmetry landscape remains largely unexplored. In this Letter, we present a systematic classification framework for unconventional magnetism based on the representation theory of the spin textures and the associated parity properties. Within this framework, we predict two previously unidentified classes beyond the established pure-parity categories: hybrid-parity magnets (HPMs) and unconstrained-parity magnets (UPMs), where the spin textures exhibit contrasting parities among their Cartesian components and the parity of the spin textures is ill-defined, respectively. We derive universal symmetry criteria that categorize HPMs into three distinct types. Importantly, by combining the spin splitting characteristics of altermagnets and odd-parity magnets, HPMs can enable the coexistence of the spin current and Edelstein effects. Taking FePO4 as an example, we perform first-principles calculations to demonstrate this coexistence. Finally, we discuss the potential applications of HPMs in spintronic devices. Our work provides a comprehensive symmetry classification of unconventional magnetism and establishes HPMs as a promising platform for multi-functional spintronics.