• DOI:10.1103/PhysRevB.96.094409
• Corpus ID: 119263427

Induced quadrupolar singlet ground state of praseodymium in a modulated pyrochlore

@article{Duijn2014InducedQS,
  title={Induced quadrupolar singlet ground state of praseodymium in a modulated pyrochlore},
  author={Joost van Duijn and K H Kim and Nam Hwi Hur and Devashibhai Thakarshibhai Adroja and F. Bridges and Aziz Daoud-Aladine and Felix Fernandez-Alonso and Roc{\'i}o Ruiz-Bustos and Jun Wen and V. Kearney and Q. Z. Huang and S. -W. Cheong and Satoru Nakatsuji and Collin L. Broholm and Toby G. Perring},
  journal={Physical Review B},
  year={2014},
  volume={96}
}

• J. V. Duijn, K. H. Kim, +12 authors T. Perring
• Published 2 July 2014
• Physics
• Physical Review B

The complex structure and magnetism of Pr$_{2-x}$Bi$_x$Ru$_2$O$_7$ 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 Pr$_2$Ir$_2$O$_7$, 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 Bi$^{3+}$. 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 T$_N$, the Ru sublattice orders antiferromagnetically, with propagation vector \textbf{k}= (0,0,0), as for Y$_2$Ru$_2$O$_7$. No ordering associated with the Pr sublattice is observed down to 100 mK. The low energy magnetic response of Pr$_{2-x}$Bi$_x$Ru$_2$O$_7$ 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.