Electronic structure and photoemission properties of EuF3 and EuCo2X2 (X=Si, Ge) compounds by ab initio methods

Electronic, magnetic and photoemission properties of the mixed-valence EuF3and EuCo2X2 compounds have been studied theoretically. Calculations have shown that europium is trivalent (4f6) in EuF3 compound. In EuCo2X2, the Eu is of intermediate valence Eu2.5+ (4f6.5). EuF3 compound is found nonmagnetic insulator. In EuCo2X2, only the europium is polarized magnetically. Photoemission (PE) measurements on EuF3 proved the exchange splitting of core s-type levels of europium even though it is in nonmagnetic (J=0) state. The calculated exchange splitting of the Eu 4s and 5s states compares quantitatively well with the observed ones