Author's Final Manuscript
Journal of Applied Physics
NiCo2O4 (NCO) films grown on MgAl2O4 (001) substrates have been studied using magnetometry, x-ray magnetic circular dichroism (XMCD) based on x-ray absorption spectroscopy, and spin-polarized inverse photoemission spectroscopy (SPIPES) with various thickness down to 1.6 nm. The magnetic behavior can be understood in terms of a layer of optimal NCO and an interfacial layer (1.2± 0.1 nm), with a small canting of magnetization at the surface. The thickness dependence of the optimal layer can be described by the finite-scaling theory with a critical exponent consistent with the high perpendicular magnetic anisotropy. The interfacial layer couples antiferromagnetically to the optimal layer, generating exchange-spring styled magnetic hysteresis in the thinnest films. The non-optimal and measurement-speed-dependent magnetic properties of the interfacial layer suggest substantial interfacial diffusion.
Mellinger, C., Wang, X., Subedi, A., Clark, A. T., Comesu, T., Rosenberg, R., Dowben, P. A., Cheng, X. and X. Xu. 2023. "Interfacial and Surface Magnetism in Epitaxial NiCo2O4(001)/MgAl2O4 Films." Journal of Applied Physics 133: 195301.