Andreev spectroscopy of CrO₂ thin films on TiO₂ and Al₂O₃

Here we analyse the spectroscopic information gathered at a number of single
CrO₂/Pb interfaces. We examine thin films requiring additional interfacial layers to generate long-range spin triplet proximity effect superconductivity (CrO₂/TiO₂) or not (CrO₂/Al₂O₃). 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. The 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.