ISIS Neutron and Muon Source Data Journal

Probing the ground state magnetism at the local scale of Pb2+/Bi3+ lone pair doped metallic pyrochlore Pr2Ir2O7 using muon-spin-rotation/relaxation

Abstract: Pyrochlore iridates host a rich ensemble of exotic quantum phases. Among them, Pr2Ir2O7 stands out as a rare metallic spin-liquid candidate exhibiting strong spin fluctuations and NFL behavior without clear long-range magnetic ordering. In this heavy-fermionic metal, the strength of Kondo and RKKY interactions are of the similar energy scales pushing the system closer to a quantum critical point. The ground state emerges from a delicate competition between Kondo screening and RKKY coupling within a geometrically frustrated lattice, where frustration further suppresses conventional magnetic ordering. Substitution of Pr3+ by Pb2+, with stereo-chemically active lone pairs, dilutes the magnetic sublattice, yields no spin freezing down to 80 mK. Conversely, Bi3+ substitution stabilizes long-range magnetic order, as muSR measurements on Bi2Ir2O7 reveal a bulk magnetic transition at Tc =1.84(3) K. These contrasting behaviors highlight the critical role of Ir4+/5+ mixed valency concentration and 4f 5d hybridization in tuning the balance between Kondo and RKKY interactions. To elucidate the microscopic nature of magnetism and spin dynamics across systems, we propose comprehensive muon spin rotation/relaxation measurements at zero-field and longitudinal-field measurements on Pr2-xPbxIr2O7-d and Pr2-xBixIr2O7-d systems down to 50 mK to map the evolution toward quantum criticality in geometrically frustrated metallic pyrochlores.

Principal Investigator: Dr Sugata Ray
Experimenter: Mr Siddhartha Sankar Soren
Experimenter: Mr Debu Das
Local Contact: Dr James Lord

DOI: 10.5286/ISIS.E.RB2610381

ISIS Experiment Number: RB2610381

Publisher: STFC ISIS Neutron and Muon Source

Data format: RAW/Nexus
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Data Citation

The recommended format for citing this dataset in a research publication is as:
[author], [date], [title], [publisher], [doi]

For Example:
Dr Sugata Ray et al; (2026): Probing the ground state magnetism at the local scale of Pb2+/Bi3+ lone pair doped metallic pyrochlore Pr2Ir2O7 using muon-spin-rotation/relaxation, STFC ISIS Neutron and Muon Source, https://doi.org/10.5286/ISIS.E.RB2610381

Data is released under the CC-BY-4.0 license.