Magnetic Phase Formation in Self-Assembled Epitaxial BiFeO[subscript 3]–MgO and BiFeO[subscript 3]–MgAl[subscript 2]O[subscript 4] Nanocomposite Films Grown by Combinatorial Pulsed Laser Deposition

摘要

Self-assembled epitaxial BiFeO[subscript 3]–MgO and BiFeO[subscript 3]–MgAl[subscript 2]O[subscript 4] nanocomposite thin films were grown on SrTiO[subscript 3] substrates by pulsed laser deposition. A two-phase columnar structure was observed for BiFeO[subscript 3]–MgO codeposition within a small window of growth parameters, in which the pillars consisted of a magnetic spinel phase (Mg,Fe)[subscript 3]O[subscript 4] within a BiFeO[subscript 3] matrix, similar to the growth of BiFeO[subscript 3]–MgFe[subscript 2]O[subscript 4] nanocomposites reported elsewhere. Further, growth of a nanocomposite with BiFeO[subscript 3]–(CoFe[subscript 2]O[subscript 4]/MgO/MgFe[subscript 2]O[subscript 4]), in which the minority phase was grown from three different targets, gave spinel pillars with a uniform (Mg,Fe,Co)[subscript 3]O[subscript 4] composition due to interdiffusion during growth, with a bifurcated shape from the merger of neighboring pillars. BiFeO[subscript 3]–MgAl[subscript 2]O[subscript 4] did not form a well-defined vertical nanocomposite in spite of having lower lattice mismatch, but instead formed a two-phase film with in which the spinel phase contained Fe. These results illustrate the redistribution of Fe between the oxide phases during oxide codeposition to form a ferrimagnetic phase from antiferromagnetic or nonmagnetic targets.