High Perpendicular Exchange Bias with a Unique Temperature Dependence in Pt/Co/$\alpha$-Cr2O3(0001) Thin Films

Perpendicular exchange bias was investigated using Pt/Co/$\alpha$-Cr 2 O 3 (0001) thin films prepared by a reactive DC magnetron sputtering method. On the $\alpha$-Cr 2 O 3 (0001) layer, the Pt/Co thin film simultaneously showed perpendicular magnetic anisotropy (PMA) and perpendicular exchange bias (PEB). Although PEB was not observed at room temperature, it suddenly appeared, accompanied by a unique temperature dependence. The suddenly appearing PEB was as large as a unidirectional magnetic anisotropy energy, $J_{\text{K}}$, of about 0.29 erg/cm 2 . The mechanism of the sudden appearance of $J_{\text{K}}$ is discussed on the basis of Meiklejohn and Bean's exchange anisotropy model.