Thermal annealing enhancement of Josephson critical currents in ferromagnetic CoFeB

TL;DR

This study demonstrates that thermal annealing significantly enhances the Josephson critical current in Nb/CoFeB/Nb devices by improving structural order, highlighting CoFeB's potential in superconducting spintronics.

Contribution

First report of superconducting devices based on CoFeB showing critical current enhancement through thermal annealing.

Findings

Critical current increased by up to 700% after annealing

Structural ordering of CoFeB improved with annealing

CoFeB is promising for superconducting spintronic applications

Abstract

The electrical and structural properties of Co40Fe40B20 (CoFeB) alloy are tunable with thermal annealing. This is key in the optimization of CoFeB-based spintronic devices, where the advantageously low magnetic coercivity, high spin polarization, and controllable magnetocrystalline anisotropy are utilised. So far, there has been no report on superconducting devices based on CoFeB. Here, we report Nb/CoFeB/Nb Josephson devices and demonstrate an enhancement of the critical current by up to 700% following thermal annealing due to increased structural ordering of the CoFeB. The results demonstrate that CoFeB is a promising material for the development of superconducting spintronic devices.