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

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 $v_F$.