# Magnetic-field-orientation-dependent triplet supercurrents in Josephson junctions with symmetric and asymmetric exchange-spring interfaces

## TL;DR

This paper demonstrates magnetic-field-dependent triplet supercurrents in Josephson junctions with exchange-spring interfaces, showing the ability to tune supercurrent propagation through ferromagnetic layers exceeding typical coherence lengths.

## Contribution

It introduces Josephson junctions with exchange-spring interfaces that enable magnetic control of triplet supercurrents over larger distances than previously possible.

## Key findings

- Supercurrents detected through Py layers over 10 nm thick.
- Magnetic inhomogeneity at Co/Py interfaces enables singlet-to-triplet conversion.
- Supercurrents are tunable by external magnetic fields.

## Abstract

Josephson junctions with s-wave superconductors (S) and multiple ferromagnetic (F) layers carry spin-triplet supercurrents in the presence of magnetically inhomogeneous spin-mixer interfaces. Here, we report magnetic Josephson junctions with exchange-spring and double exchange-spring ("spin-mixer") Co/Py interfaces. At the Co/Py interface, exchange coupling is strong with respect to the magnetic anisotropy of Py and so, depending on the direction and magnitude of an external magnetic field, a non-collinear magnetic structure forms in Py creating the necessary magnetic inhomogeneity for singlet-to-triplet pair conversion. We detect supercurrents through Py with a thickness exceeding 10 nm, which is much larger than the singlet pair coherence length, suggesting the propagation of magnetically tuneable triplet supercurrents.