Spin polarization of magnetoresistive materials by point contact spectroscopy

Abstract

In the strive to find a straightforward method for determining the spin polarization, the analysis of the Andreev reflection process in point contact junctions has attracted much interest. However, the prerequisite for an evaluation of the transport spin polarization in this scheme is the existence of elastic (ballistic or diffusive) transport, which cannot be assumed a priori. We therefore also include inelastic processes in our analysis and exemplify that thermal effects can have a significant effect on data evaluation. As ferromagnetic samples with a predicted half metallic behavior and comparably low conductivity we used thin films of the double perovskite ${\mathrm{Sr}}_2{\mathrm{FeMoO}}_6$ and bulk material of the Heusler compound ${\mathrm{Co}}_2{\mathrm{Cr}}_{0.6}{\mathrm{Fe}}_{0.4}\mathrm{Al}.$