Anisotropic resistive switching in Fe₃O₄ thin films on stepped MgO substrates: Influence of electric field orientation and temperature dependence

Magnetite (Fe₃O₄) thin films were epitaxially grown on stepped MgO(100) substrates to investigate resistive switching (RS) behavior in the presence of surface steps. The films exhibited hysteresis in current-voltage (I-V) measurements below the Verwey transition temperature (T_V ≈ 120 K), revealing anisotropic RS behavior depending on the direction of the applied electric field. When the electric field was applied parallel to the surface steps, stable switching was observed with over 16 000 cycles at 95 K, without degradation. In contrast, when the field was applied perpendicular to the steps, switching was observed down to 85 K. However, at 80 K, the device showed complete failure due to the interaction of the electric field with antiphase boundary defects along the steps. These findings highlight the role of surface morphology in modulating RS behavior and provide insights into the mechanisms governing RS in Fe₃O₄, consistent with theoretical predictions of charge gap closure under an applied electric field. The results emphasize the significance of substrate steps in controlling the RS characteristics of magnetite thin films.