The Stoner instability has long been recognized as a fundamental concept in the understanding of metallic ferromagnetic materials, capturing the interplay of Coulomb repulsion, Pauli exclusion, and twofold fermionic spin degeneracy. This paradigm was extended by demonstrating that the Stoner instability can be harnessed to generate unconventional magnetism, a class of magnetic materials characterized by momentum-dependent spin splitting.

These findings have far-reaching implications for the field of spintronics. This study finds that pseudospin can carry unexpected symmetries that precludes it from coupling to a Zeeman field. This phenomenon exists in materials with spin–orbit coupling and appears at the Brillouin zone boundary. With Coulomb repulsion, this spinless pseudospin phenomenon gives rise to Stoner instabilities into unconventional magnetism.