Correlation between Spin Polarization and Magnetic Moment in Ferromagnetic Alloys

TL;DR

This paper investigates the relationship between spin polarization and magnetic moments in ferromagnetic alloys, revealing that s-electron density of states polarization correlates with magnetic moments, explaining experimental observations.

Contribution

It introduces a CPA-based model showing s-electron polarization correlates with magnetic moments, clarifying experimental results not explained by net density of states.

Findings

Spin polarization of s-electrons correlates with magnetic moments.

Net density of states polarization does not correlate with magnetic moments.

Discrepancies between tunneling and Andreev reflection measurements are discussed.

Abstract

The correlation between the magnetic moment in ferromagnetic alloys and the tunneling spin polarization in ferromagnet-insulator-superconductor tunneling experiments has been a mystery. The measured spin polarization for Fe, Co, Ni, and various Ni alloys is positive and roughly proportional to their magnetic moments, which can not be explained by considering the net density of states. Using a tight-binding coherent potential approximation (CPA) model, we show that while the polarization of the net density of states is not correlated with the magnetic moment, the polarization of the density of states of {\it s} electrons is correlated with the magnetic moment in the same manner as observed by the tunneling experiments. We also discuss the spin polarization measurements by Andreev reflection experiments, some of which obtained different results from the tunneling experiments and our calculations.