Weak quasistatic magnetism in the frustrated Kondo lattice Pr_2Ir_2O_7

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.

arXiv comment4 pages, 3 figures, to appear in Proc. 11th Int. Conf. on Muon Spin Rotation, Relaxation and Resonance (muSR2008)

References in corpus (5)

• Metal-Nonmetal Changeover in Pyrochlore Iridates
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• Spin-Glass-like Transition and Hall Resistivity of Y2-xBixIr2O7
• Muon spin relaxation and hyperfine-enhanced 141Pr nuclear spin dynamic in Pr(Os,Ru)4Sb12 and (Pr,La)Os4Sb12
• Inhomogeneous level splitting in Pr${}_{2-x}$Bi${}_x$Ru${}_2$O${}_7$

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