Topology and chemistry of competing interactions in tetravalent lanthanides
Author(s)
Ramanathan, Arun
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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 highvalent
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.
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Date
2023-04-27
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Dissertation