Rock-salt type superconductor/ferromagnet heteroepitaxial junction: LaO/EuO

We report the first synthesis of rock-salt type superconductor/ferromagnet heteroepitaxial junctions using ferromagnetic semiconductor EuO [1]. As the superconducting layer, we deposited LaO with the maximum T_c of 5.2 K onto EuO. The small lattice mismatch made it possible to synthesize a high-quality heteroepitaxial junction with an atomically sharp interface that realizes the ideal magnetic proximity effect. The magnetization of LaO/EuO heteroepitaxial junctions was governed by the ferromagnetic EuO layer. The saturation magnetization of 7 μ_B/Eu atom at 5 K was equivalent to that of EuO thin film. Owing to the sharp interface and the strong magnetization, superconductivity in 21 nm thick LaO layer was fully suppressed by only 6 nm thick EuO layer. This system can be used for a new heteroepitaxial platform of superconducting spintronics devices. [1] K. Kaminaga et al., Chem. Lett. 48, 1244 (2019).