On the nature of spin reorientation transition thermal hysteresis in NiO(111)/Fe(110) bilayers.

We report on temperature-driven in-plane 90° magnetization switching in NiO(111)/Fe(110) bilayer epitaxially grown on a W(110) single crystal, investigated using magneto-optical Kerr effect and X-ray magnetic circular and linear dichroism measurements. As the temperature varies, an abrupt switching of the easy axis between the in-plane Fe[001] and Fe[Formula: see text] crystallographic directions is observed. In the temperature range of approximately 210-285 K, a thermal hysteresis region appears, where two energy minima coexist at a given temperature. Our experimental findings are supported by phenomenological modeling. Simulations incorporating temperature-dependent anisotropy constants successfully reproduce the key features of the observed phenomenon, most notably the temperature-driven hysteresis of ferromagnetic magnetization switching. The spin reorientation transition in both exchange-coupled ferromagnetic and antiferromagnetic layers is driven by the interplay between magnetocrystalline and interfacial magnetic anisotropies in the ferromagnet, which stabilizes specific magnetization orientation at given temperature.