Spin-dependent band structure of the ferromagnetic semimetal EuB$_{6}$

The spin polarization of EuB$_{6}$ crystals has been measured using Andreev reflection spectroscopy. The conductance spectra of the EuB$_{6}$/Pb junctions are well-described by the spin-polarized BTK model, which yields a spin polarization of about 56{\%}. The results demonstrate that ferromagnetic EuB$_{6}$ is not half-metallic. Further analyses of the Hall effect and magnetoresistivity indicate a semi-metallic band structure with complete spin polarization for the hole band only. The values and the spread of the measured spin polarization are \textit{quantitatively} consistent with Fermi surface determined by quantum oscillation measurements$^{1}$ and carrier densities obtained from standard two-band model fits to the low temperature magnetoresistivity and Hall resistivity. This work was supported by a FSU Research Foundation PEG, NSF DMR 0710492 and 0503360 grants. $^{1}$R. Goodrich et al., PRB \textbf{58}, 14896 (1998); M. Aronson et al., PRB \textbf{59}, 4720 (1999).