Demonstration of magnetoelectric effect in ultrathin Cr ₂O ₃/Fe ₂O ₃ nano-oxide layer by training effect

We identified magnetoelectric effect in an ultrathin (Cr ₂O ₃/Fe ₂O ₃) nano-oxide layer structure (thickness ∼1 nm) formed on the surface of a Co _0.9Fe _0.1 metal layer by investigating the training effect as a function of sense current/bias voltage and its direction. A system-dependent constant κ _MR, which reflects changes in the surface spin, increases (decreases) with increasing current in the pinned (inverse pinned) direction. Furthermore, κ _MR varies for temperatures up to ∼200 K with current despite the extreme thinness, thus suggesting the current contributes to the surface spin changes. The results indicate the demonstration of the magnetoelectric effect in ultrathin Cr ₂O ₃.