Structural and magneto-transport properties of lattice-mismatched epitaxial Fe/SrO/MgO/Fe magnetic tunnel junctions

Abstract

We investigated the structural and magneto-transport properties of Fe/SrO/MgO/Fe magnetic tunnel junctions (MTJs), in which SrO has a large lattice mismatch (Δa/a ∼ 21%) with Fe. Despite such a large Δa/a, structural analyses revealed that a fully epitaxial Fe(001)/SrO(001)/MgO(001)/Fe(001) structure was successfully formed. We observed high magnetoresistance (MR) ratios up to 98% at 20 K (65% at room temperature), suggesting that coherent spin-polarized tunneling occurs through the SrO(001) tunnel barrier. We also demonstrated that the resistance-area product and bias-voltage (Vhalf), at which the MR ratio reaches half of the zero-bias value, were comparable to the values reported in epitaxial Fe/MgO/Fe MTJs. Since SrO has a smaller Δa/a with Si (∼5%) than that between MgO and Si (∼23%), the results offer that this material is a promising candidate as a high-quality tunnel barrier for Si-based spin transport devices.