Why are there so few non-altermagnetic antiferromagnets?

TL;DR

This paper reviews the conditions influencing spin splitting in antiferromagnets, proposing that spin splitting is common unless specific criteria prevent it, and discusses properties of antiferromagnets that maintain spin degeneracy.

Contribution

It introduces criteria for when antiferromagnets preserve spin degeneracy, highlighting conditions that prevent non-relativistic spin splitting.

Findings

Spin splitting is the default in magnetically ordered systems.

Certain antiferromagnets preserve spin degeneracy due to specific properties.

The paper outlines criteria to identify systems that avoid spin splitting.

Abstract

We review the conditions that cause or prohibit non-relativistic spin splitting of the energy bands in antiferromagnets. We propose that the existence of spin splitting in magnetically ordered systems is the default scenario and outline the criteria that must be met to avoid it. We discuss some of the properties of those special antiferromagnets that succeed in preserving their spin degeneracy.