Superconducting Spin Valve in the Solitary Superconductivity Regime

Superconducting spin valve heterostructures of the F1/F2/S design, consisting of superconducting (S) and ferromagnetic (F) layers, have been studied in order to detect the theoretically predicted state of solitary superconductivity. This state is characterized by the occurrence of superconductivity only at the antiparallel magnetizations of the ferromagnetic layers. In this work, owing to optimally selected design parameters of the superconducting spin valve, the state of solitary superconductivity has been experimentally realized for the first time. An anomalously large spin valve effect Δ T_c = T_c^AP - T_c^P > 0.2 K, which can reach a value of 1.6 K in a magnetic field of 1 kOe, has been detected in an HA/HA/Pb superconducting spin valve (where HA is a Heusler alloy Co 2 Cr 1 – x Fe x Al). Until now, comparable results in terms of the superconducting spin valve effect have been observed only in structures with triplet superconductivity in external magnetic fields significantly exceeding 1 kOe. The obtained results open new prospects for the development of superconducting current control devices.