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The thermal conductivity of single crystals of iron-doped quartz and lithium niobate between 1K and 300K, and the magnetization of iron-doped quartz

The thermal conductivity of single crystals of iron-doped quartz and lithium niobate between 1K and 300K, and the magnetization of iron-doped quartz
The thermal conductivity of single crystals of iron-doped quartz and lithium niobate between 1K and 300K, and the magnetization of iron-doped quartz

The thermal conductivity of a quartz crystal doped with iron has been measured between 1.8K and 300K. An enormous decrease in the conductivity was observed, compared with that of a pure quartz crystal, the phonon mean free path in the temperature region below the conductivity maximum being less by a factorof about 5,000. This large reduction in conductivity is attributed to phonon scattering by iron colloids. The thermal conductivity results have been analysed using the phenomenological theory developed by Callaway; this analysis gives a value for the colloid radius of about 2.3 nm. The magnetization of the iron-doped quartz crystal has been measured as a function of applied field and temperature. Superparamagnetic behaviour was observed, and the colloid size distribution obtained by fitting a modified Langevin function to the magnetization curve. The colloid radii were found to vary between 1-4 nm, a mean value being 2.1 nm, in good agreement with the result obtained by analysis of the thermal conductivity data. The thermal conductivity of a lithium niobate crystal has been measured between 1.7K and 80K, both prior and subsequent to the production of a space-charge grating in the crystal. The presence of the grating was seen to produce a reduction in the conductivity at temperatures below that of the conductivity maximum, the maximum reduction observed being about 40% at the lowest temperatures measured.

University of Southampton
Daniels, Michael Edward
Daniels, Michael Edward

Daniels, Michael Edward (1981) The thermal conductivity of single crystals of iron-doped quartz and lithium niobate between 1K and 300K, and the magnetization of iron-doped quartz. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The thermal conductivity of a quartz crystal doped with iron has been measured between 1.8K and 300K. An enormous decrease in the conductivity was observed, compared with that of a pure quartz crystal, the phonon mean free path in the temperature region below the conductivity maximum being less by a factorof about 5,000. This large reduction in conductivity is attributed to phonon scattering by iron colloids. The thermal conductivity results have been analysed using the phenomenological theory developed by Callaway; this analysis gives a value for the colloid radius of about 2.3 nm. The magnetization of the iron-doped quartz crystal has been measured as a function of applied field and temperature. Superparamagnetic behaviour was observed, and the colloid size distribution obtained by fitting a modified Langevin function to the magnetization curve. The colloid radii were found to vary between 1-4 nm, a mean value being 2.1 nm, in good agreement with the result obtained by analysis of the thermal conductivity data. The thermal conductivity of a lithium niobate crystal has been measured between 1.7K and 80K, both prior and subsequent to the production of a space-charge grating in the crystal. The presence of the grating was seen to produce a reduction in the conductivity at temperatures below that of the conductivity maximum, the maximum reduction observed being about 40% at the lowest temperatures measured.

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Published date: 1981

Identifiers

Local EPrints ID: 460462
URI: http://eprints.soton.ac.uk/id/eprint/460462
PURE UUID: 2bc691c5-0107-48ac-9cf8-b92df258f507

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Date deposited: 04 Jul 2022 18:22
Last modified: 04 Jul 2022 18:22

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Author: Michael Edward Daniels

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