Spin-Polarized Splittings in the Temperature-Dependent Reflectance of EuO

The reflectance of EuO from above the Curie point at 69°K down to 1.5°K shows splittings in the two main peaks near 1.5 and 4.7 eV. The first peak is a polarization-dependent triplet at 1.5°K and a doublet at 70°K. The data suggest that the 1.5-eV peak is associated with the absorption edge and arises from the transition $4f^7\left({}_{}{}^8{}_{}{}^{}S_{\frac{7}{2}}^{}{}_{}{}^{}\right)\to 4f^6\left({}_{}{}^7{}_{}{}^{}F_J^{}{}_{}{}^{}\right)5d\left(t_{2g}\right)$. The narrow $t_{2g}$ sub-band is exchange split by 0.25 eV at low temperatures.