Andreev spectroscopy of CrO$_{2}$ thin films on TiO$_{2}$ and Al$_{2}$O$_{3}$

Abstract

Here we analyse the spectroscopic information gathered at a number of single CrO$_{2}$ / Pb interfaces. We examine thin films requiring additional interfacial layers to generate long range spin triplet proximity effect superconductivity (CrO$_{2}$/TiO$_{2}$) or not (CrO$_{2}$/Al$_{2}$O$_{3}$). We analyse the data using two theoretical models and explore the use of a parameter free method to determine the agreement between the models and experimental observations, showing the necessary temperature range that would be required to make a definitive statement. The use of the excess current as a further tool to distinguish between models is also examined. Analysis of the spectra demonstrates that the temperature dependence of the normalised zero bias conductance is independent of the substrate onto which the films are grown. This result has important implications for the engineering of interfaces required for the long range spin triplet proximity effect.