Magnetotransport Signatures of a Multi-Regime Electronic Transition in V₄O₇ Thin Films

Vanadium oxides exhibit a rich interplay between structural distortions and electronic transport. Among them, V₄O₇ is particularly intriguing due to its intermediate stoichiometry between VO₂ and V₂O₃, where both electron correlation and lattice effects are comparably strong. We investigate the temperature- and field-dependent longitudinal and transverse resistances of lithographically defined V₄O₇ Hall-bar devices fabricated from epitaxial thin films. The longitudinal resistivity ρ_L(T) displays two anomalies: a pronounced feature near 230 K, consistent with an insulator–metal transition (IMT), and a secondary kink around 140 K marking a crossover to a distinct low-temperature transport regime. Below 140 K, ln (ρ_L) varies linearly with T/T₀ (T₀ ≈ 10 K), indicating a non-Arrhenius conduction process. Magnetoresistance measurements reveal three regimes: a low-T quadratic MR ∝ B², a chaotic intermediate region (130–208 K), and a high-T quadratic regime restored above 212 K. The MR slope S(T) follows ln(S) ∝ –T/T₀ (T₀ ≈ 50 K) with a local maximum near 230 K, coincident with the IMT feature. These results indicate strong coupling between structural strain, carrier localization, and magnetic-field response in V₄O₇, placing it between VO₂-like Peierls behavior and V₂O₃-like correlation-driven transport.