Observation of the dominant spin-triplet supercurrent in Josephson spin valves with strong Ni ferromagnets

TL;DR

This study demonstrates the generation of dominant spin-triplet supercurrent in Josephson spin-valves with strong Ni ferromagnets, revealing a triplet current three times larger than the singlet supercurrent through experimental techniques.

Contribution

It provides experimental evidence and characterization techniques for spin-triplet superconductivity in Ni-based Josephson spin-valves, a novel finding in superconductor-ferromagnet systems.

Findings

Spin-triplet supercurrent is approximately three times larger than the singlet supercurrent.

Anomalous Ic(H) patterns correlate with magnetic states of the spin-valve.

Micromagnetic characterization techniques reveal the relationship between magnetic configuration and supercurrent.

Abstract

We study experimentally nanoscale Josephson junctions and Josephson spin-valves containing strong Ni ferromagnets. We observe that in contrast to junctions, spin valves with the same geometry exhibit anomalous Ic(H) patterns with two peaks separated by a dip. We develop several techniques for in-situ characterization of micromagnetic states in our nano-devices, including magnetoresistance, absolute Josephson fluxometry and First-Order-Reversal-Curves analysis. They reveal a clear correlation of the dip in supercurrent with the antiparallel state of a spin-valve and the peaks with two noncollinear magnetic states, thus providing evidence for generation of spin-triplet superconductivity. A quantitative analysis brings us to a conclusion that the triplet current in out Ni-based spin-valves is approximately three times larger than the conventional singlet supercurrent.