Direct Measurements of Spin-Dependent and Coherent Effects in Conductance of a Ferromagnet/Superconductor System

Abstract

In the systems ferromagnet/superconductor ([Fe, Ni]/In), the temperature dependent transport has been investigated within the temperature range including superconducting transition temperature for Indium. It has been found that when Indium becomes superconducting, the system resistance acquires two positive additions. The first, numerically equal to the resistance of a ferromagnet part, of order of a spin--polarized region in length, corresponds to the manifestation of "spin accumulation" effect. The second agrees in magnitude with an interference reduction in the ferromagnet conductance over the coherence length for singlet "Andreev pairs" which is established by the exchange field in the ferromagnet. From the experimental data, the degree of current spin polarization, the coherence length in the exchange field, and the lower limit of spin--relaxation length in Fe and Ni have been estimated.