Substrate Surface Roughness-Induced Antiphase Boundaries and Strain Relaxation in Cufe2o4 Films on Mgal2o4 (001) Substrates

Spinel ferrites have great potential applications in microwave devices and spintronics because of their high saturation magnetization, high spin polarization and low loss performance at high frequencies [1]. Among the spinel ferrites, CuFe2O4 has been widely investigated due to its interesting physical properties. CuFe2O4 has two structural polymorphs: a high-temperature cubic and a low-temperature tetragonal. The Cu2+ ions tend to occupy octahedral sites and the Fe3+ ions occupy both octahedral and tetrahedral sites. It was found that cation distribution and phase stability of CuFe2O4 can be affected by the growth parameters for the thin-film fabrication, which induces a profound impact on the magnetic, electric and optical properties of the films [2]. In addition, antiphase boundaries (APBs) in epitaxial films have significant effects on the physical properties. Recently, it was reported that the rough substrate can introduce APBs into the functional oxide films [3]. In this work, we investigate the microstructure of epitaxial CuFe2O4 films on rough MgAl2O4 (001) substrates. Our studies mainly focus on the origin of APBs and strain relaxation in the CuFe2O4/MgAl2O4 (001) system.