Nondeteriorating Verwey Transition in 50 nm Thick Fe₃O₄ Films by Virtue of Atomically Flattened MgO Substrates: Implications for Magnetoresistive Devices

Perfect surfaces can upgrade the quality of the films grown on them and ensure that their physical properties do not deteriorate. Here, an atomically flattened surface is homogeneously formed over an entire MgO(001) substrate by an original chemical polishing technique. The atomically flattened substrate enabled a nondeteriorating Verwey transition to be induced in a 50 nm thick Fe3O4 thin film on the substrate because of the extremely low defect density and high homogeneity of the film. The maximum relative change in resistivity was ∼6, which is almost a one-order improvement, which was due to the atomically flattened substrate. Additionally, a statistical evaluation shows that the changes in resistivity and transition temperatures across the Verwey transition shift toward higher values. The result clearly shows the effectiveness of a substrate surface with both atomic flatness and high crystallinity in suppressing the variation in a characteristic among samples, leading to the development of high-performance magnetoresistive devices to manifest the materials’ potential physical properties.