Enhancement of Josephson Critical Currents in Ferromagnetic Co40 Fe40 B20 by Thermal Annealing

The electrical and structural properties of Co40Fe40B20 (Co-Fe-B) are tunable by thermal annealing. This is key to the optimization of Co-Fe-B-based spintronic devices, where the advantageously low magnetic coercivity, high spin polarization, and controllable magnetocrystalline anisotropy are utilized. Here, we report Nb/Co-Fe-B/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 Co-Fe-B. The results demonstrate that Co-Fe-B is a promising material for superconducting quantum spintronic devices.