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arXiv · 0808.3142

Weak quasistatic magnetism in the frustrated Kondo lattice Pr_2Ir_2O_7

D. E. MacLaughlin·Y. Ohta·Y. Machida·S. Nakatsuji·G. M. Luke·K. Ishida·R. H. Heffner·Lei Shu·O. O. Bernal
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Abstract

Muon spin relaxation experiments have been performed in the pyrochlore iridate Pr_2Ir_2O_7 for temperatures in the range 0.025-250 K. Kubo-Toyabe relaxation functions are observed up to > 200 K, indicating static magnetism over this temperature range. The T -> 0 static muon spin relaxation rate Delta(0) ~ 8 mus^-1 implies a weak quasistatic moment (~0.1 mu_B). The temperature dependence of Delta is highly non-mean-field-like, decreasing smoothly by orders of magnitude but remaining nonzero below ~150 K. The data rule out ordering of the full Pr^3+ CEF ground-state moment (3.0 mu_B) down to 0.025 K. The weak static magnetism is most likely due to hyperfine-enhanced ^141Pr nuclear magnetism. The dynamic relaxation rate lambda increases markedly below ~20 K, probably due to slowing down of spin fluctuations in the spin-liquid state. At low temperatures lambda is strong and temperature-independent, indicative of a high density of low-lying spin excitations as is common in frustrated antiferromagnets.

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D. E. MacLaughlin, Y. Ohta, Y. Machida, S. Nakatsuji, G. M. Luke, K. Ishida, R. H. Heffner, Lei Shu, O. O. Bernal. 2008-08-22. Weak quasistatic magnetism in the frustrated Kondo lattice Pr_2Ir_2O_7. https://doi.org/10.1016/j.physb.2008.11.167

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