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Persistent URL http://purl.org/net/epubs/work/17697245
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Record Id 17697245
Title Quadrupolar Singlet Ground State of Praseodymium in a Modulated Pyrochlore
Abstract The complex structure and magnetism of Pr2?xBixRu2O7 was investigated by neutron scattering and EXAFS. Pr has an approximate doublet ground-state and the first excited state is a singlet. This overall crystal field level scheme is similar to metallic Pr2Ir2O7, which is also reported here. While the B-site (Ru) is well ordered throughout, this is not the case for the A-site (Pr/Bi). A distribution of the Pr-O2 bond length indicates the Pr environment is not uniform even for x=0. The Bi environment is highly disordered ostensibly due to the 6s lone pairs on Bi3+. Correspondingly we find the non-Kramers doublet ground state degeneracy otherwise anticipated for Pr in the pyrochlore structure is lifted so as to produce a quadrupolar singlet ground state with a spatially varying energy gap. For x=0, below TN, the Ru sublattice orders antiferromagnetically, with propagation vector \textbf{k}= (0,0,0), as for Y2Ru2O7. No ordering associated with the Pr sublattice is observed down to 100 mK. The low energy magnetic response of Pr2?xBixRu2O7 features a broad spectrum of magnetic excitations associated with inhomogeneous splitting of the Pr quasi-doublet ground state. For x=0 (x=0.97) the spectrum is temperature dependent (independent). It appears disorder associated with Bi alloying enhances the inhomogeneous Pr crystal field level splitting so that inter-site interactions become irrelevant for x=0.97. The structural complexity for the A-site may be reflected in the hysteretic uniform magnetization of B-site ruthenium in the N\'{e}el phase.
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Language English (EN)
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Journal Article Phys Rev B (2015). http://arxiv.org/abs/1407.0661 2015