Reduced magnetocrystalline anisotropy of CoFe2O4 thin films studied by angle-dependent x-ray magnetic circular dichroism

Spinel-type CoFe$_2$O$_4$ is a ferrimagnetic insulator with the N\'eel temperature exceeding 790 K, and shows strong cubic magnetocrystalline anisotropy (MCA) in bulk materials. However, when film grown on other materials, its magnetic properties are degraded so that so-called magnetically dead layers expected to be formed interfacial region. We investigate how of modified at interface CoFe$_2$O$_4$/Al$_2$O$_3$ bilayers Si(111) using x-ray circular dichroism (XMCD). find thinner films have significantly smaller MCA values than The reduction explained by reduced number Co$^{2+}$ ions $O_h$ site reported previous study [Y. K. Wakabayashi $\textit{et al.}$, Phys. Rev. B $\textbf{96}$, 104410 (2017)].