Much more to explore with an oxidation state of nearly four: Pr valence instability in intermetallic m-Pr2Co3Ge5

Trent M Kyrk; Ellis R Kennedy; Jorge Galeano-Cabral; Gregory T McCandless; Mary C Scott; Ryan E Baumbach; Julia Y Chan

doi:10.1126/sciadv.adl2818

Much more to explore with an oxidation state of nearly four: Pr valence instability in intermetallic m-Pr₂Co₃Ge₅

Sci Adv. 2024 Jan 26;10(4):eadl2818. doi: 10.1126/sciadv.adl2818. Epub 2024 Jan 26.

Authors

Trent M Kyrk¹, Ellis R Kennedy², Jorge Galeano-Cabral^{3

4}, Gregory T McCandless¹, Mary C Scott^{2

5

6}, Ryan E Baumbach^{4

7}, Julia Y Chan¹

Affiliations

¹ Department of Chemistry and Biochemistry, Baylor University, Waco, TX 76706, USA.
² Department of Materials Science and Engineering, Univeristy of California, Berkeley, Berkeley, CA 94720, USA.
³ FAMU-FSU College of Engineering, Department of Mechanical Engineering, Florida State University, Tallahassee, FL 32310, USA.
⁴ National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA.
⁵ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁶ National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁷ Department of Physics, Florida State University, Tallahassee, FL 32310, USA.

Abstract

For some intermetallic compounds containing lanthanides, structural transitions can result in intermediate electronic states between trivalency and tetravalency; however, this is rarely observed for praseodymium compounds. The dominant trivalency of praseodymium limits potential discoveries of emergent quantum states in itinerant 4f¹ systems accessible using Pr⁴⁺-based compounds. Here, we use in situ powder x-ray diffraction and in situ electron energy-loss spectroscopy (EELS) to identify an intermetallic example of a dominantly Pr⁴⁺ state in the polymorphic system Pr₂Co₃Ge₅. The structure-valence transition from a nearly full Pr⁴⁺ electronic state to a typical Pr³⁺ state shows the potential of Pr-based intermetallic compounds to host valence-unstable states and provides an opportunity to discover previously unknown quantum phenomena. In addition, this work emphasizes the need for complementary techniques like EELS when evaluating the magnetic and electronic properties of Pr intermetallic systems to reveal details easily overlooked when relying on bulk magnetic measurements alone.