Trivalent europium - a scarce case in intermetallics

In most intermetallic europium compounds, the Eu atoms exhibit a divalent oxidation state with a high effective magnetic moment since Eu2+ is isoelectronic with Gd3+. Trivalent intermetallic Eu compounds, in contrast, are extremely scarce and under 20 examples are known to literature. This mini-review summarizes the known binary and ternary examples along with their crystal-chemical peculiarities as well as their magnetic and Eu-151 Mossbauer spectroscopic behavior. Additionally, compounds that exhibit valence phase transitions are summarized.

Automated summary

In most europium compounds, Eu atoms are in the divalent oxidation state and have a high effective magnetic moment due to the isoelectronic relationship between Eu2+ and Gd3+. However, trivalent intermetallic Eu compounds are extremely rare, with less than 20 examples known in the literature. This mini-review provides a summary of the known binary and ternary Eu compounds, highlighting their crystal-chemical characteristics, magnetic properties, Eu-151 Mossbauer spectroscopic behavior, and valence phase transitions.