The spin-filter properties of a Cu-EuO-Cu junction have been investigated using density functional theory by N. Jutong et al. [ Phys. Rev. B 86, 205310 (2012)]. The results indicate that EuO epitaxially grown on Cu can act as an almost perfect spin filter, with a spin polarization of the current close to 100%. The figure shows how the I-V curve depends on the EuO thickness.