Magnetic Precursor to the Structural Phase Transition in V2O3

The coupling between structural, electronic and magnetic degrees of freedom across the metal-insulator transition in V₂O₃ makes it hard to determine the main driving mechanism behind the transition. Specifically, the role of magnetism is debated and its interplay with the other transitions has not been established. To address this issue, this work uses a combination of muon spin relaxation/rotation, electrical transport and reciprocal space mapping which allows to correlate magnetic, electronic and structural degrees of freedom in strain-engineered V₂O₃ thin films. Evidence is found for a magnetic instability in the vicinity of the structural transition. This is manifested as a decrease in the antiferromagnetic moment in proximity to the structural and electronic transitions. Moreover, this work finds evidence for an onset of antiferromagnetic (AF) fluctuations in the rhombohedral phase even without a structural transition to the monoclinic phase. In samples where the transition is most strongly suppressed by strain, a depth-dependent magnetic state is observed. These results reveal the importance of an AF instability in the paramagnetic phase in triggering the metal-insulator transition and the crucial role of the structural transition in allowing for the formation of an ordered AF state.