Metallic Ferrimagnetism and Magnetic Domain Structure in (001) NiCo2O4 Films Grown at Various Temperatures

Epitaxial 31-nm-thick (001) NiCo2O4 films exhibiting metallic and ferrimagnetic properties at room temperature were grown on (001) MgAl2O4 substrates at various deposition temperatures. theta/2 theta scan and reciprocal space mapping X-ray diffraction measurements indicated that tetragonal lattice distortion in the (001) NiCo2O4 films increased with the deposition temperature. Metallic ferrimagnetism and perpendicular magnetic anisotropy (PMA) were observed for (001) NiCo2O4 films grown at deposition temperatures below 350 degrees C. Remarkably, the ferrimagnetic transition temperature continuously decreased with increasing deposition temperature up to 350 degrees C, whereas images of the magnetic domains indicated that the density of the nucleated small domains during the early stage of magnetic reversal increased with the deposition temperature. Consequently, the PMA of the (001) NiCo2O4 films at room temperature was optimized using a deposition temperature of approximately 320 degrees C. The results of this study indicate that the deposition temperature is a useful parameter for adjusting the PMA and magnetic domain structure of NiCo2O4 films by inducing variations in structural distortion and metallic ferrimagnetism.