Phase Formation and Exchange Bias in LuFeO₃–CoxFe3–xO₄ Nanocomposite Films

Vertically aligned nanocomposite thin films comprising antiferromagnetic and ferroelectric LuFeO3 and ferrimagnetic CoxFe3–xO4 are synthesized by a codeposition method using pulsed laser deposition from two or three targets of different composition. The phases that form (perovskite, spinel, and rocksalt), their compositions, and the magnetic anisotropy of the nanocomposites are strongly influenced by the selection of targets from the group of Lu-rich LuFeO3, Fe-rich LuFeO3, CoFe2O4, and Co3O4. When the Co and Fe are delivered from different targets, the spinel crystals have a range of compositions. Owing to the crystallographic relationship between the perovskite LuFeO3 and spinel CoxFe3–xO4 in the nanocomposites, a negative exchange bias of −5.3 mT at room temperature is demonstrated upon field cooling a 31 nm thick LuFeO3–Co1.2Fe1.8O4 film.