Use of Mesoscopic Host Matrix to Induce Ferrimagnetism in Antiferromagnetic Spinel Oxide

摘要

Despite the advances in the methods for fabricating nanoscale materials, critical issues remain, such as the difficulties encountered in anchoring, and the deterioration in their stability after integration with other components. These issues need to be addressed to further increase the scope of their applicability. In this study, using epitaxial mesoscopic host matrices, materials are spatially confined at the nanoscale, and are supported, anchored, and stabilized. They also exhibit properties distinct from the bulk counterparts proving their high quality nanoscale nature. ZnFe2O4 and SrTiO3 are used as the model confined material and host matrix, respectively. The ZnFe2O4 phases are spatially confined by the SrTiO3 mesoscopic matrix and have strongly enhanced ferrimagnetic properties as compared to bulk and plain thin films of ZnFe2O4, with a Curie temperature of approximate to 500 K. The results of a series of control experiments and characterization measurements indicate that cationic inversion, which originates from the high interface-to-volume ratio of the ZnFe2O4 phase in the ZnFe2O4-SrTiO3 nanocomposite film, is responsible for the magnetization enhancement. An exchange bias is observed, owing to the coexistence of ferrimagnetic and antiferromagnetic regions in the confined ZnFe2O4 phase. The magnetic properties are dependent on the ZnFe2O4 crystallite size, which can be controlled by the growth conditions.