Bulk Spin Polarization of Co$_{(1-x)}$Fe$_x$S$_2$

TL;DR

This study introduces a novel method combining magnetic Compton scattering and ab initio calculations to accurately measure bulk spin polarization in Co$_{(1-x)}$Fe$_x$S$_2$, revealing significant spin polarization variations with Fe doping.

Contribution

The paper presents a new approach to determine bulk spin polarization using magnetic Compton profiles refined by ab initio calculations, applicable to single crystal Co$_{(1-x)}$Fe$_x$S$_2$.

Findings

Measured spin polarization: -72% for CoS$_2$ and 18% for Co$_{0.9}$Fe$_{0.1}$S$_2$.

Refined calculations match experimental profiles, enabling accurate P extraction.

Demonstrated dependence of P on Fermi velocity, facilitating comparison with other data.

Abstract

We report on a new method to determine the degree of bulk spin polarization in single crystal Co$_{(1-x)}$Fe$_x$S$_2$ by modeling magnetic Compton scattering with {\it ab initio} calculations. Spin-dependent Compton profiles were measured for CoS$_2$ and Co$_{0.9}$Fe$_{0.1}$S$_2$. The {\it ab initio} calculations were then refined by rigidly shifting the bands to provide the best fit between the calculated and experimental directional profiles for each sample. The bulk spin polarizations, $P$, corresponding to the spin-polarized density of states at the Fermi level, were then extracted from the {\it refined} calculations. The values were found to be $P=-72 \pm 6 %$ and $P=18 \pm 7%$ for CoS$_2$ and Co$_{0.9}$Fe$_{0.1}$S$_2$ respectively. Furthermore, determinations of $P$ weighted by the Fermi velocity ($v_F$ or $v_F^2$) were obtained, permitting a rigorous comparison with other experimental data and highlighting the experimental dependence of $P$ on $v_F$.