Electric Tuning of Magnetic Anisotropy and Exchange Bias of La0.8Sr0.2CoO3/La0.67Sr0.33MnO3 Bilayer Films

Heterostructures composed of dissimilar perovskite oxides with different properties provide an opportunity to observe emergent phenomena, and have promising applications. A key feature of oxide heterostructures is interfacial electronic and orbital reconstruction. In this paper, we demonstrate a dramatic variation in magnetic anisotropy caused by electric tuning of the charge-transfer process in a La0.8Sr0.2CoO3/La0.67Sr0.33MnO3 bilayer structure. By repeatedly changing the valence state of Co ions in the La0.8Sr0.2CoO3 top layer using ionic-liquid gating, reversible switching of the magnetic easy axis of the bottom La0.67Sr0.33MnO3 layer between the out-of-plane and the in-plane direction is achieved, accompanying a modulation of the interfacial exchange coupling. Mn-to-Co charge transfer and its effect on the interfacial orbital occupancy are further confirmed by x-ray absorption spectroscopy and x-ray-linear-dichroism analysis. The considerable interfacial charge transfer causes an overlap of the Mn and Co 3d orbitals, resulting in orbital reconstruction in the La0.67Sr0.33MnO3 layer and thus magnetic anisotropy. This work demonstrates a promising method for tuning the orbital occupancy and related properties of perovskite heterostructures.