Temperature dependence of transport spin polarization in NdNi5 measured using Point Contact Andreev reflection

TL;DR

This study investigates how the transport spin polarization in NdNi5 varies with temperature near its Curie point using Point Contact Andreev Reflection spectroscopy, revealing a correlation with magnetization and spin fluctuations.

Contribution

It provides the first detailed temperature-dependent measurements of transport spin polarization in NdNi5 across its ferromagnetic transition.

Findings

Spin polarization follows spontaneous magnetization with temperature.

Superconducting quasiparticle lifetime decreases near Curie temperature.

Strong ferromagnetic spin fluctuations are observed close to TC.

Abstract

We report a study in which Point contact Andreev reflection (PCAR) spectroscopy using superconducting Nb tip has been carried out on NdNi5, a ferromagnet with a Curie temperature of TC~7.7K. The measurements were carried out over a temperature range of 2-9K which spans across the ferromagnetic transition temperature. From an analysis of the spectra, we show that (i) the temperature dependence of the extracted value of transport spin polarization closely follows the temperature dependence of the spontaneous magnetization; (ii) the superconducting quasiparticle lifetime shows a large decrease close to the Curie temperature of the ferromagnet. We attribute the latter to the presence of strong ferromagnetic spin fluctuations in the ferromagnet close to the ferromagnetic transition temperature.