Nontrivial anomalous Hall effect in ultrathin Pt/permalloy bilayers

Anomalous Hall effect of Pt (2.5 nm)/permalloy bilayers with the thickness t$_{\mathrm{Py}}=$ 0.6$\sim $10 nm; Pt/permalloy (2.2 nm) bilayers with the thickness t$_{\mathrm{Pt}}=$ 1.5$\sim $10 nm and Pt (2.5 nm)/permalloy (2.2 nm) bilayers with the post-annealing temperature 100$\sim $500${^\circ}$ grown on MgO (001) substrates are investigated. The Pt/permalloy bilayer shows distinguished performance from the single permalloy layer due to the interfacial influence. Effective magnetic anisotropy of the bilayer with t$_{\mathrm{Py}}$ \textless 2.2 nm turns to be perpendicular to the film plane and it increases with decreasing measured temperature. More interestingly, the anomalous Hall effect is also greatly enhanced in these Pt/permalloy bilayers, comparing with that in bulk permalloy. The parameters presenting skew scattering, side jump and intrinsic contribution become extremely large, indicating a strong influence of spin orbit coupling coming from Pt/permalloy interface on the anomalous Hall effect.