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

The reflectance of EuO from above the Curie point at 69\ifmmode^\circ\else\textdegree\fi{}K down to 1.5\ifmmode^\circ\else\textdegree\fi{}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\ifmmode^\circ\else\textdegree\fi{}K and a doublet at 70\ifmmode^\circ\else\textdegree\fi{}K. The data suggest that the 1.5-eV peak is associated with the absorption edge and arises from the transition $4{f}^{7}(^{8}S_{\frac{7}{2}})\ensuremath{\rightarrow}4{f}^{6}(^{7}F_{J})5d({t}_{2g})$. The narrow ${t}_{2g}$ sub-band is exchange split by 0.25 eV at low temperatures.