Spin-triplet supercurrents in Josephson junctions with Co/Py exchange-spring interfaces
Abstract
Conventional (spin-singlet) s-wave superconductivity (S) and ferromagnetism (F) are incompatible. However, it is now established that s-wave S can coexist with F through the conversion of spin-singlet to spin-triplet Cooper pairs at a magnetically inhomogeneous interface. Here we report Josephson coupling in Nb/Co/Py/Nb Josephson junctions in which the total bilayer (Co/Py) thickness exceeds the singlet pair coherence length [1nm in Py). At a Co/Py interface, the interface exchange coupling is strong compared to the weak magnetic anisotropy of Py and so, depending on the direction and magnitude of an external magnetic field, an in-plane Bloch domain wall can form in Py creating the necessary magnetic non-collinearity for pair conversion. We observe Josephson coupling for Py layer thicknesses up to 11 nm which greatly exceeds the singlet coherence length, strongly suggesting the propagation of spin-polarized triplet supercurrents. Furthermore, through magnetic field history we are able to programme the magnetic state, which offers the potential for active control of triplet supercurrents.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- 2019
- Bibcode:
- 2019APS..MARL09012B