Andreev current and subgap conductance of spin-valve SFF structures

The Andreev current and the subgap conductance in a superconductor/ insulator/ ferromagnet (SIF) structure in the presence of a small spin-splitting field show novel interesting features [1]. For example, the Andreev current at zero temperature can be enhanced by a spin-splitting field h, smaller than the superconducting gap ∆ , as has been recently reported by the authors. Also at finite temperatures the Andreev current has a peak for values of the spin-splitting field close to the superconducting gap, h ≈ ∆ . Finally, the differential subgap conductance at low temperatures show a peak at the bias voltage eV = h. In this paper we investigate the Andreev current and the subgap conductance in SFF structures with arbitrary direction of magnetization of the F layers. We show that all aforementioned features occur now at the value of the “effective field”, which is the field acting on the Cooper pairs in the multi-domain ferromagnetic region, averaged over the decay length of the superconducting condensate into a ferromagnet. We also briefly discuss the A. S. Vasenko Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble, France E-mail: [email protected] A. Ozaeta · F. S. Bergeret Centro de Fı́sica de Materiales (CFM-MPC), Centro Mixto CSIC-UPV/EHU, Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; Donostia International Physics Center (DIPC), Manuel de Lardizabal 4, E-20018 San Sebastián, Spain S. Kawabata Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Tsukuba, Ibaraki 305-8568, Japan F. W. J. Hekking NLPMMC, Université Joseph Fourier and CNRS, 25 Avenue des Martyrs, BP 166, 38042 Grenoble, France heat transport and electron cooling in the considered structures.