Chemical Design of Electronic and Magnetic Energy Scales in Tetravalent Praseodymium

TL;DR

This paper reveals that praseodymium in the 4+ oxidation state exhibits unusual bonding and magnetic properties due to 4f orbital participation, challenging traditional ionic models and opening new avenues in quantum material research.

Contribution

It demonstrates the breakdown of the ionic paradigm for Pr4+ and uncovers its unique hybridization and magnetic behavior through experimental and theoretical analysis.

Findings

Pr4+ shows 4f orbital participation in bonding.

Pr4+ exhibits hybridization similar to transition metals.

The magnetic behavior departs from the Jeff=1/2 limit.

Abstract

Lanthanides in the trivalent oxidation state are typically described using an ionic picture that leads to localized magnetic moments. The hierarchical energy scales associated with trivalent lanthanides produce desirable properties for e.g., molecular magnetism, quantum materials, and quantum transduction. Here, we show that this traditional ionic paradigm breaks down for praseodymium in the 4+ oxidation state. Synthetic, spectroscopic, and theoretical tools deployed on several solid-state Pr4+ oxides uncover the unusual participation of 4f orbitals in bonding and the anomalous hybridization of the 4f1 configuration with ligand valence electrons, analogous to transition metals. The resulting competition between crystal-field and spin-orbit-coupling interactions fundamentally transforms the spin-orbital magnetism of Pr4+, which departs from the Jeff =1/2 limit and resembles that of high-valent actinides. Our results show that Pr4+ ions are in a class on their own, where the hierarchy of single-ion energy scales can be tailored to explore new correlated phenomena in quantum materials.