Preparation and characteristics of 90° rotated biepitaxial Fe3O4 thin films

In-plane 90degrees rotated biepitaxial Fe3O4 thin films have been successfully prepared onto MgO (110) substrates using a CeO2 seed layer and their microstructure, electric, and magnetic properties were investigated. From the x-ray p-scan measurements, the in-plane epitaxial relations were determined as <110>Fe3O4//<110>MgO and <001>Fe2O4//<001>MgO for the no-seeded Fe3O4 layer, and <001>Fe3O4//<110>MgO and <110>Fe3O4//<001>MgO for the CeO2 (110) seeded Fe3O4 layer. The CeO2 seed layer was found to rotate the upper Fe3O4 lattice at 90degrees upon normal axis to the layer against the no-seeded Fe3O4. The transmission electron microscopy and electron diffraction analyses revealed that the transition region of the biepitaxial Fe3O4 boundary between CeO2-seeded and no-seeded portions consisted of columnarlike polycrystalline grains. The Fe3O4 films exhibited single-crystallinelike electric and magnetic properties, however, substantial spin-dependent-tunneling magnetoresistance across the 90degrees grain boundary was not observed even in the antiparallel situation for each Fe3O4 portion.