Superconducting triplet spin valve

Abstract

We study the critical temperature T c of SFF trilayers (S is a singlet superconductor, F is a ferromagnetic metal), where the long-range triplet superconducting component is generated at noncollinear magnetizations of the F layers. We demonstrate that T c can be a nonmonotonic function of the angle α between the magnetizations of the two F layers. The minimum is achieved at an intermediate α, lying between the parallel (P, α = 0) and antiparallel (AP, α = π) cases. This implies a possibility of a “triplet” spin-valve effect: at temperatures above the minimum T Tr c but below T P c and T AP c , the system is superconducting only in the vicinity of the collinear orientations. At certain parameters, we predict a reentrant T c (α) behavior. At the same time, considering only the P and AP orientations, we find that both the “standard” (T P c < T AP c ) and “inverse” (T P c > T AP c ) switching effects are possible depending on parameters of the system.