Crystal symmetry predicts unconventional magnetism

Abstract

Unconventional compensated magnets combine zero net magnetization with momentum-dependent spin polarization, but identifying them usually requires knowledge of their magnetic order. Here we show that crystal symmetry can constrain unconventional magnetic character before the magnetic ground state is known. Starting from a non-magnetic crystal structure and a specified magnetic sublattice, we generate symmetry-compatible compensated orders and classify their spin textures using spin-space-group symmetry. We identify materials whose generated candidates are all unconventional, either across a defined search space or after restricting the magnetic-cell size. Within the experimental benchmark, 68% of the prioritized materials are unconventional, compared with 9% of the remaining materials. Screening the Materials Project yields thousands of promising candidates for unconventional compensated magnetism. First-principles calculations for $\mathrm{VGe_3}$ and tetragonal $\mathrm{Fe_2SiO_4}$ connect these symmetry predictions to the energetics and spin textures of competing magnetic orders. In $\mathrm{VGe_3}$, a noncoplanar candidate permits mixed-wave spin polarization along a fixed axis without spin-orbit coupling, combining components that are odd and even under momentum reversal. This framework enables crystallography-guided searches for unconventional compensated magnets without first determining their magnetic ground states.