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The thermal conductivities of high-purity cerium magnesium nitrate and lanthanum magnesium nitrate single crystals have been measured in zero or small magnetic fields. The phonon mean free path is found to be limited by processes intrinsic to the crystal. This mean free path can be longer than nominally allowed by the dimensions of the specimen. Measurements were also made on samples doped with other rare-earth ions. The resonant absorption of phonons by the non-Kramers ions Pr and Ho is observed and is shown to result from electronic transitions between hyperfine energy levels.
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Robichaux et al. (1970) studied this question.
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