Competition of perpendicular magnetic anisotropy and exchange magnetic anisotropy in a Pt/Co/α-Cr 2 O 3 (0001) thin film

We investigated perpendicular magnetic anisotropy and exchange magnetic anisotropy in a Pt/Co/α-Cr 2 O 3 (0001) thin film grown on an α-Al 2 O 3 (0001) substrate. The film exhibits perpendicular magnetic anisotropy below a Co thickness of 1.2 nm at room temperature. Independent of the magnetic easy direction of the Co layer, the perpendicular exchange bias (PEB) appears in a direction perpendicular to the film below 80 K. The maximum unidirectional magnetic anisotropy energy estimated from the exchange bias field is 0.33 erg/cm 2 , which is higher than the reported PEB strength. The perpendicular exchange bias is accompanied by the in-plane remanent magnetization and an increase in the in-plane coercivity. We speculate that the increases in the in-plane remanent magnetization and the in-plane coercivity are caused by the spin canting of Cr 3+ in the α-Cr 2 O 3 (0001) layer.