Electronic structure and optical spectroscopy studies of HoNi5 and ErNi5 compounds doped with Cu

The effect of Cu‐doping on the electronic structure and optical properties of intermetallic compounds (Ho,Er)Ni5−xCux (x = 0, 1, 2) has been studied. Band structure and interband optical conductivity were investigated theoretically using the LSDA + U method supplementing local spin density approximation with a correction for strong electron interaction on the 4f shell of rare earth element. Optical properties were studied by the ellipsometry method in the spectral range 0.22–15 µm. It was found that substitution of Cu for Ni atoms in these alloys leads to significant changes in the frequency dependence of the optical conductivity. Both the theoretical calculations and spectroscopic experiments revealed the appearance of a new absorption maximum near 4.5 eV formed by Cu 3d → Ni 3d interband transitions.