Andreev reflection at ferromagnet/superconductor interfaces

Andreev reflection is a scattering process where electrical current is converted to supercurrent where there is an interface between a normal metal and a superconductor. Recently, much attention has been focused on Andreev reflection in nanohybrids of ferromagnet (F) and superconductor (S). This is for a variety of reasons. Andreev reflection in a F-S point contact provides a powerful tool for determining the spin polarization of conducting electrons. The coherence length of a superconductor can be estimated by measuring the tunnel magnetoresistance of a F-S-F double junction system. A novel scattering process called crossed Andreev reflection can be predicted for a superconductor with two ferromagnetic leads, where Andreev reflection occurs even if the ferromagnetic leads are half metallic. In this chapter the theory of Andreev reflection in nanohybrids of F and S is introduced, and recent progress in this field is reviewed.