Perpendicular Magnetic Anisotropy of an Ultrathin Fe Layer Grown on NiO(001)

The magnetic anisotropy and magnetic interactions at the interface between Fe and NiO(001) were investigated. Depending on the growth conditions of the NiO(001) layers and the postannealing tem-perature, the preferential magnetization direction of the ultrathin Fe layer grown on a NiO(001) layer changed from the in-plane direction to a direction perpendicular to the film plane. The lattice constant of the NiO(001) layers parallel to the growth direction increased with O2 flow rate, while that parallel to the in-plane direction were locked onto the MgO(001) substrate regardless of the growth conditions of the NiO layers. Moreover, perpendicular magnetization was observed only when the NiO layer was grown with O2 flow rates higher than 2.0 sccm corresponding to oxygen-rich NiO. X-ray magnetic circular dichroism measurements revealed an enhancement in anisotropic orbital magnetic moments similar to the origin of perpendicular magnetic anisotropy at the Fe/MgO(001) interface. The interfacial magnetic anisotropy energies were 0.93 and 1.02 mJ/m2 at room temperature and at 100 K, respectively, indicating less temper-ature dependence. In contrast, the coercivity Hc exhibited a significant temperature dependence. Although no signature of exchange bias or unidirectional loop shift was observed, Hc was strongly dependent on the NiO layer thickness, indicating that the exchange interaction at the interface between the ferromagnetic and antiferromagnetic layers was not negligible, despite the NiO(001) being a spin-compensated surface.

Automated summary

The study investigates the magnetic anisotropy and magnetic interactions at the interface between Fe and NiO(001). The preferential magnetization direction of the ultrathin Fe layer on NiO(001) changed depending on the growth conditions and post-annealing temperature. The lattice constant of NiO(001) layers parallel to the growth direction increased with O2 flow rate, while those parallel to the in-plane direction were locked onto the MgO(001) substrate. Perpendicular magnetization was observed only when the NiO layer was grown with high O2 flow rates. The magnetic anisotropy energies at the interface were temperature-independent, while the coercivity exhibited a significant temperature dependence. The exchange interaction between the ferromagnetic and antiferromagnetic layers was not negligible, despite NiO(001) being a spin-compensated surface.