Competition between Anti-Phase Boundaries and Charge-Orbital Ordering in Epitaxial Stepped Fe₃O₄(100) Thin Films

Magnetite is a highly utilized transition metal oxide with many interesting magnetic and transport properties. The presence of anti-phase boundaries (APBs) and charge-orbital ordering (COO) are two of the most exciting properties of epitaxial magnetite thin films. Here, epitaxial stepped Fe₃O₄ films were prepared to investigate the competition between APBs and COO via measurements of in-plane anisotropy. The anisotropy was probed for two orthogonal configurations, with magnetic field applied or electrical-contacts aligned either along or perpendicular to the steps. We reveal that the APBs dominate the magnetic and transport properties of the films above the Verwey transition temperature (TV). However, below TV film thickness becomes a decisive factor in determining the magnetic nature of stepped magnetite films, due to its correlation with domain size. When the film is thinner than a critical thickness, the anisotropy is dominated by the APBs, and a higher anisotropy constant and MR ratio are observed when the magnetic field or contacts are oriented along the steps. Conversely, for sufficiently thick films, below TV, the magnetic and electrical transport properties are dominated by COO. Thus a higher anisotropy constant and MR ratio are observed when the magnetic field or contacts are oriented perpendicular to the steps.