Bistable and absolute switching driven by superconducting exchange coupling.

As per de Gennes' predictions, a superconducting layer placed between two ferromagnetic insulators can drive an antiferromagnetic exchange coupling between them. Using two ferromagnetic insulating GdN layers having dissimilar switching fields sandwiching a superconducting Vanadium thin film, we demonstrate evidence of such exchange coupling. We demonstrate that such an exchange coupling promotes switching between zero and finite resistance states of Vanadium. Our devices hold either a finite resistance or a zero-resistance state at zero magnetic field, dependent on their magnetic field history. Moreover, we demonstrate the absolute switching effect, thus making such devices suitable for application at the lowest temperatures as non-volatile cryogenic memory useful for futuristic quantum circuits and for several other superconducting spintronic applications.