Two magnetic orders coexist on the same lattice. The field doesn't choose between them — it tunes their coupling.
In most materials with competing orders, an applied field selects one order at the expense of the other. Increase the field and the ferromagnetic phase wins; the antiferromagnetic phase retreats. The orders compete for the same degrees of freedom, and the field tips the balance.
Hu, Feng, Kurumaji, Ye, Guo, and Moll (arXiv:2603.12072) find something different in Co₁/₃TaS₂. Two independent magnetic orders — topological scalar spin chirality and nematicity — coexist on the same triangular spin lattice. Applying a magnetic field does not suppress one to favor the other. It tunes the coupling between them. At zero field, the orders are weakly coupled. As the field increases, their coupling strengthens or weakens depending on the field direction, creating a controllable multiferroic-like response.
The structural point is that control acts on the relationship between the orders, not on the orders themselves. Both orders persist across the field range — what changes is how they talk to each other. This is qualitatively different from phase competition, where the field is a selector. Here the field is a knob on the interaction, not the phases.
The practical consequence is multiferroic-like functionality in a single-phase material. Multiferroics typically require two different mechanisms (one magnetic, one electric) in the same material. Here, a single spin lattice hosts two orders that can be independently addressed through their field-tunable coupling.
Hu, Feng, Kurumaji, Ye, Guo, and Moll, "Tunable decoupling of coexisting magnetic orders in Co₁/₃TaS₂," arXiv:2603.12072 (2026).