Signature of metal–metal bonding in Ir–Ni–Ta–(B) bulk metallic glasses

In bulk metallic glasses, minimizing the total electronic energy is a key factor in glass formation. However, it remains unclear how this energy is minimized, particularly in metallic glasses made up of transition metal elements. In this study, we use synchrotron-based photoemission spectroscopy to investigate the electronic structure of Ir–Ni–Ta–(B) bulk metallic glasses, which are primarily composed of transition metals and have recently been discovered to exhibit exceptional glass-forming ability. We observe distinct chemical shifts in the core levels of Ir and Ta in opposite directions, while the Ni is close to an elemental-like state, suggesting significant Ir–Ta charge transfer and metal–metal bonding in the metallic glass phase. Additionally, a pseudogap at EF suggests an additional contribution from the itinerant electrons to the glass-forming ability, but likely playing a secondary role as it is only observed in Ir35Ni20Ta40B5. Our findings highlight the critical role of metal–metal bonding in facilitating the glass formation of metallic glasses composed of transition metals.