We investigated the spin polarization P of Co-based Heusler alloy Co2FeSi by epitaxial contact Andreev reflection (ECAR) spectroscopy using epitaxially grown superconductor NbN and Heusler alloy Co2FeSi layered devices. Ferromagnetic Co2FeSi possesses the highest Curie temperature (TC ≈ 1100 K) and the largest spontaneous magnetic moment (ps ≈ 6 μB) in the class of Heusler alloys. The ECAR measurements revealed that the P value of Co2FeSi was 54 ± 2% with a finite barrier parameter Z, indicating that an intrinsic P value in ECAR spectroscopy would exceed reported values in point-contact Andreev reflection spectroscopy. We therefore established not only the epitaxial integration of ferromagnetic Co2FeSi with superconductor NbN on an MgO substrate but also the fabrication and evaluation techniques of their ECAR devices. This highly versatile superconducting spintronic system enables fundamental superconducting spintronic studies, and it is also a candidate for practical superconducting spintronic devices.

中文翻译：

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NbN/Co2FeSi 层状器件的外延接触 Andreev 反射光谱

我们使用外延生长的超导体 NbN 和 Heusler 合金 Co2FeSi 层状器件通过外延接触 Andreev 反射（ECAR）光谱研究了 Co 基 Heusler 合金 Co2FeSi 的自旋极化 P。铁磁 Co2FeSi 在 Heusler 合金类中拥有最高的居里温度 (TC ≈ 1100 K) 和最大的自发磁矩 (ps ≈ 6 μB)。ECAR 测量显示 Co2FeSi 的 P 值为 54±2%，具有有限的势垒参数 Z，表明 ECAR 光谱中的固有 P 值将超过点接触 Andreev 反射光谱中报告的值。因此，我们不仅建立了铁磁 Co2FeSi 与超导体 NbN 在 MgO 衬底上的外延集成，而且还建立了它们的 ECAR 器件的制造和评估技术。