Andreev reflections and magnetoresistance in ferromagnet-superconductor mesoscopic structures

An analysis is made of the change in the resistance of a nanostructure consisting of a diffusive ferromagnetic (F) wire and normal metal electrodes, due to the onset of superconductivity (S) in the normal electrode and Andreev scattering processes. The superconducting transition results in an additional contact resistance arising from the necessity to match the spin-polarized current in the F-wire to the spinless current in the S reservoir, which is comparable to the resistance of a piece of F wire with length equal to the spin relaxation length. It is also shown that in the absence of spin relaxation the resistance of a two-domain structure is the same for a ferro- or antiferromagnetic configuration if one electrode is in the superconducting state. (C) 1999 American Institute of Physics. [S0021-3640(99)00707-0].