Unconventional Antiferromagnets - Beyond Conventional Antiferromagnets

Antiferromagnets are an important class of magnetically ordered materials due to compensation of the magnetic moments. They are increasingly important for emerging spintronic technologies, as they can enable greater data density, faster devices, and new functionality. Traditionally, the magnetic-moment compensation arises from symmetry constraints (translation and inversion). Recently, several new paradigms enabling the development of antiferromagnets have emerged and are discussed in this Viewpoint. These include compensated ferrimagnets, altermagnets, and artificial/synthetic antiferromagnets as well as antiferromagnetically ordered ferri- and ferromagnets, as they offer additional pathways to discover new antiferromagnets with new phenomena and technologically important attributes. Additionally, the magnetic ordering Néel temperature, TN, is frequently reported as the maximum temperature in the susceptibility, χ(T), data; however, the maximum temperature in the d[χ(T)T]/dT data (so-called Fisher specific heat) is in better agreement with the specific-heat determined TN and is preferred.