Investigation of local structural and magnetic properties of discontinuous to continuous layer of Co at Co/MgO interface in MgO/Co/MgO trilayer structure

Abstract

We investigate influence of oxygen migration in MgO/Co/MgO trilayer structure by varying Co and MgO layer thickness. To resolve Co/MgO interface structural and magnetic properties, we used near edge X-ray absorption spectra (XANES), X-ray absorption fine structure (XAFS) spectroscopy and Magneto-optical Kerr effect (MOKE) on MgO/Co/MgO trilayer structure. O K-edge XANES spectra show the variation in hybridization of Co 3d orbitals with neighboring O 2p orbitals as a function of Co layer thickness. Co L3 -edge XANES and Co K-edge XAFS results revealed the quantity of CoO formation as a function of Co layer thickness from discontinuous layer to continuous layer. Formation of cobalt oxide is mainly due to island formation of Co ≤ 10 nm layer and oxygen migration from MgO layer at interface via redox reaction to form CoO bonds. The oxygen migration is driven by imperfect stoichiometry of MgO at the Co/MgO interface. The formation of CoO layer influences the CoO orbital hybridization modifying in-plane magnetic anisotropy as a function of Co and MgO layer thickness. Higher coercivity (Hc) for lower thickness of Co layer confirms the formation of domain wall pinning. A model has been drawn to describe the interaction of Co layer with MgO layer at Co/MgO interface from discontinues to continuous region of Co thin film of magnetic tunnel junctions (MTJ)s, which may help to design high-performance spintronic devices.