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Onset of antiferromagnetism in UPt_{3} via Th-substitution studied by muon spin spectroscopy

M. J. Graf·A. de Visser·C. P. Opeil·J. C. Cooley·J. L. Smith·A. Amato·C. Baines·F. Gygax·A. Schenck
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Abstract

Muon spin spectroscopy has been used to study in detail the onset of large-moment antiferromagnetism (LMAF) in UPt_{3} as induced by Th substitution. Zero-field experiments have been carried out on a series of polycrystalline U_{1-x}Th_{x}Pt_{3} (0 <= x <= 0.05) samples in the temperature range 0.04 - 10 K. At low Th content (x <= 0.002) magnetic ordering on the time scale of the uSR experiment (10^{-8} s) is not detected. For x = 0.005 a weak magnetic signal appears below T = 2 K, while for 0.006 <= x <= 0.05, spontaneous oscillations in the uSR spectra signal the presence of the LMAF phase. The data are well described by a two-component depolarization function, combining the contribution of a polycrystalline antiferromagnet and a Kubo-Lorentzian response. However, the transition into the antiferromagnetic phase is quite broad. For x = 0.01 and 0.02, a weak magnetic signal appears below about 7 K, which is well above the mean-field transition temperatures. The broadening may be a result of the effects of disorder on the time fluctuations associated with anomalous small-moment antiferromagnetism.

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M. J. Graf, A. de Visser, C. P. Opeil, J. C. Cooley, J. L. Smith, A. Amato, C. Baines, F. Gygax, A. Schenck. 2003-11-06. Onset of antiferromagnetism in UPt_{3} via Th-substitution studied by muon spin spectroscopy. https://doi.org/10.1103/physrevb.68.224421

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