Exchange coupling mechanisms at ferromagnetic/CoO interfaces

The nature of the interfacial exchange between a ferromagnetic (FM) metal film and an antiferromagnetic oxide film was investigated in FM (30 nm)/CoO (30 nm) bilayer films, with the FM materials Fe, Co, Ni, Ni₈₀Fe₂₀, and Ni₅₀Co₅₀. FM materials with a high Ni concentration exhibit reduced values of net unidirectional interfacial exchange energy density, {Δ}{σ}. Mean-field analysis predicts the variation in {Δ}{σ} and indicates that the interfacial coupling occurs via direct exchange between metal atoms. An alternative, possibly coexisting mechanism involves plausible interfacial chemical reactions.