This thesis examines two aspects of superconducting phenomena by employing two different experimental techniques. The first phenomenon is two-gap superconductivity, and the second phenomenon is long-range proximity induced spin-triplet (LRPST) superconductivity.
Using point contact Andreev reflection (PCAR) spectroscopy, evidence for two-gap superconductivity was investigated in Mo1-xRex alloys. Recent specific heat capacity measurements claim the existence of two-gap superconductivity in these alloys. PCAR spectroscopy can identify superconducting energy gaps, and was used here to see if two-gap superconductivity could be confirmed. Direct observation of two distinct energy gaps in spectra measured at 4.2 K and 2 K was not found. However, comparing the temperature dependent PCAR parameters extracted from a single-gap fit with a two-gap fit to the spectra offered some interesting insight.
PCAR spectroscopy was also used to investigate the second phenomenon. In superconductor/ferromagnet (S/F) structures, it is possible to create LRPST with long-range penetration in F by having a spatially inhomogeneous magnetic layer at the interface. This interface is known as a ‘spin-active’ interface, where spin-mixing and spin-rotation processes can occur. Stimulated by claims that a paramagnetic Meissner effect, carried by spin-triplets, can be observed in Nb/Ho/Au multilayers, PCAR was used here to see if signatures of proximity induced spin-triplets could be observed. Theoretical calculations have predicted that spin-mixing at the spin-active interface can lead to Andreev bound states that appear as sub-gap features in electrical conductance spectra. Furthermore, LRPST may also give rise to a peak in the density of states at zero energy.
Finally, a ferromagnetic resonance (FMR) technique was used to see if LRPST could be detected in a non-equilibrium system. Nb/Cr/Fe/Cr/Nb multilayers were studied, where it was found that the key signature of a spin-triplet channel was observed only when the correct conditions were satisfied in the presence of an externally applied field.