Interfacial Spin-Orbit Coupling: A Platform for Superconducting Spintronics

Isidoro Martínez (1) , Petra Högl (2) , César González-Ruano (1) , Juan Pedro Cascales (3) , Coriolan Tiusan (4) , Yuan Lu (5) , Michel Hehn (5) , Alex Matos-Abiague (6) , Jaroslav Fabian (2) , Igor Žutić (2) , Farkhad G Aliev (1)

1 UAM - Universidad Autónoma de Madrid
2 University of Regensburg
3 MIT - Massachusetts Institute of Technology
4 Technical University of Cluj-Napoca
5 IJL - Institut Jean Lamour
6 Wayne State University [Detroit]

Spin-orbit coupling (SOC) is a key interaction in spintronics, allowing electrical control of spin or mag-netization and, vice versa, magnetic control of electrical current. However, recent advances have revealed much broader implications of SOC that is also central to the design of topological states with potential applications from low-energy dissipation and faster magnetization switching to high tolerance of disorder. SOC and the resulting emergent interfacial spin-orbit fields are simply realized in junctions through structural inversion asymmetry, while the anisotropy in magnetoresistance (MR) allows their experimental detection. Surprisingly, we demonstrate that an all-epitaxial ferromagnet/MgO/metal junction with a single ferromagnetic region and only negligible MR anisotropy undergoes a remarkable transformation below the superconducting transition temperature of the metal. The superconducting junction has a MR anisotropy 3 orders of magnitude higher and could enable novel applications in superconducting spin-tronics. In contrast to common realizations of MR effects that require a finite applied magnetic field, our system is designed to have two stable zero-field states with mutually orthogonal magnetizations: in plane and out of plane. This bistable magnetic anisotropy allows us to rule out orbital and vortex effects due to an applied magnetic field and identify the SOC origin of the observed MR. Such MR reaches approximately 20% without an applied magnetic field and could be further increased for large magnetic fields that support vortices. Our findings call for a revisit of the role of SOC, even when it seems negligible in the normal state, and suggest an alternative platform for superconducting spintronics.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Isidoro Martínez, Petra Högl, César González-Ruano, Juan Pedro Cascales, Coriolan Tiusan, et al.. Interfacial Spin-Orbit Coupling: A Platform for Superconducting Spintronics. Physical Review Applied, 2020, 13 (1), ⟨10.1103/PhysRevApplied.13.014030⟩. ⟨hal-02999602⟩