Magnetic-field-induced color change in α -Fe 2 O 3 single crystals

We investigated the magneto-optical properties of $\ensuremath{\alpha}$-Fe${}_{2}$O${}_{3}$ in order to understand the interplay between charge and magnetism in a model transition metal oxide. We discovered that hematite appears more red in applied magnetic field than in zero-field conditions, an effect that is amplified by the presence of the spin-flop transition. Analysis of the exciton pattern on the edge of the d-d color band reveals $C2$ monoclinic symmetry in the high-field phase. These findings advance our understanding of magnetoelectric coupling away from the static limit and motivate spectroscopic work on other iron-based materials under extreme conditions.