ISSN:
1434-6036
Keywords:
PACS. 76.80.+y Mössbauer effect, other γ-ray spectroscopies – 75.50.Ee Antiferromagnetics – 75.40.Gb Dynamic properties – 05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract: Using 155Gd Mössbauer spectroscopy down to 27 mK, we show that, in the geometrically frustrated pyrochlore Gd2Sn2O7, the Gd3+ hyperfine levels are populated out of equilibrium. From this, we deduce that the hyperfine field, and the correlated Gd3+ moments which produce this field, continue to fluctuate as T ↦ 0. With a model of a spin 1/2 system experiencing a magnetic field which reverses randomly in time, we obtain an analytical expression for the steady state probability distribution of the level populations. This distribution is a simple function of the ratio of the nuclear spin relaxation time to the average electronic spin-flip time. In Gd2Sn2O7, we find the two time scales are of the same order of magnitude. We discuss the mechanism giving rise to the nuclear spin relaxation and the influence of the electronic spin fluctuations on the hyperfine specific heat. The corresponding low temperature measurements in Gd2Ti2O7 are presented and discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1140/epjb/e2002-00165-2
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