Electronic structure of Pd42.5Ni7.5Cu30P20, an excellent bulk metallic glass former: Comparison to the Pd40Ni40P20 reference glass

In-house photoemission and inverse-photoemission spectra (PES and IPES) were measured on Pd42.5Ni7.5Cu30P20 and Pd40Ni40P20 bulk metallic glasses in order to clarify the origin of excellent glass-forming ability from the viewpoint of electronic structure. Minima are observed for both the metallic glasses at a slightly higher energy than the Fermi level. Incident photon-energy dependent PES spectra were obtained using synchrotron radiation and the Pd 4d partial density of states (DOS) was estimated from the PES data. Soft X-ray emission spectra were also measured near the Ni and Cu 2p3/2 absorption edges to evaluate, respectively, the Ni and Cu 3d partial DOS in the valence band. The Pd 4d and the Ni and Cu 3d partials in the conduction band were obtained from X-ray absorption spectra around the Pd 3p3/2 and Ni and Cu 2p3/2 absorption edges, respectively. It was found that the Pd 4d partial DOS near the Fermi energy largely decreases and becomes localized by replacing the Ni atoms with the Cu atoms, which may be closely related to the excellent glass-forming ability of the Pd42.5Ni7.5Cu30P20 bulk metallic glass due to a selective formation of Pd–P covalent bonds.