superconductorferromagnetsuperconductor
Superconductor–ferromagnet–superconductor (SFS) junctions are a class of Josephson devices in which a ferromagnetic metal layer is sandwiched between two superconducting electrodes. They rely on the superconducting proximity effect, where superconducting correlations penetrate the ferromagnet, decaying and simultaneously oscillating due to the exchange field in the ferromagnet. This leads to a Josephson coupling that can adopt either a 0-phase or a π-phase, depending on factors such as the ferromagnet thickness, material properties, and temperature. Consequently, the critical current can oscillate with the ferromagnet thickness and even change sign, signaling a 0–π transition.
Materials commonly used in SFS junctions include superconductors such as niobium (Nb) and ferromagnetic metals or
In addition to conventional singlet proximity effects, SFS junctions with noncollinear magnetizations in multilayer structures can
Applications include tunable π-junctions for superconducting qubits, rapid single flux quantum circuits, and superconducting spintronic devices.