Exploring interfacial magnetism in all-spinel Fe₃O₄/MgCr₂O₄/Fe₃O₄ epitaxial heterostructures

Epitaxial heterostructures integrating thin Fe₃O₄ films hold great potential for spintronics, magnetoionics, and multifunctional device development. In this work, the morpho-structural and magnetic properties of all-spinel Fe₃O₄/MgCr₂O₄/Fe₃O₄ trilayers grown on an MgCr₂O₄ buffer layer, exhibiting very close lattice matching, were investigated using both surface- and bulk-sensitive techniques. The close lattice match between Fe₃O₄ and MgCr₂O₄ enables the growth of epitaxial heterostructures with magnetically decoupled Fe₃O₄ layers for spacer thicknesses of ≥1.6 nm, while reducing the formation of antiphase boundaries. Despite localized interphase diffusion, which leads to the formation of a mixed Cr/Fe spinel oxide with magnetically polarized Cr ions at the Fe₃O₄/MgCr₂O₄ interfaces, the overall magnetic properties remain largely consistent with those of the individual Fe₃O₄ layers. This study sheds light on the magnetic interactions within Fe₃O₄ layers mediated by an MgCr₂O₄ spacer and demonstrates the feasibility of the approach in preserving the properties of thin Fe₃O₄ films in complex heterostructures, thus offering a promising pathway for designing advanced all-spinel oxide devices.