We report the study of structural phase transitions in La0.4Ce0.6Co2P2 and EuCo2P2. Both compounds are characterized by the ThCr2Si2-type structure, which undergoes a structural collapse along the tetragonal c axis upon lowering temperature or applying external pressure, respectively. A traditional approach to describing such phase transitions is based on the assumption that the oxidation state of Ce or Eu is increased under pressure (Ce3+ → Ce4+ or Eu2+ → Eu3+), while the formation of the P–P bond in the collapsed structure also contributes to the increase in the oxidation state of phosphorus from –3 to –2, according to the Zintl-Klemm formalism. As a result of such changes, the electron density should be transferred to the Co atoms. Using various structural and spectroscopic techniques combined with theoretical methods, we demonstrate that such simplistic view does not provide an adequate description of the realistic changes in the electronic structure of these materials. Moreover, we show the formation of unconventional spin-glass state in the collapsed structure of La0.4Ce0.6Co2P2.

Understanding magneto-structural phase transitions in Ce- and Eu-containing intermetallics: Inadequacy of formal oxidation states

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.