Excess specific heat of KCl crystals caused by randomly distributed OH- dipole impurities

The peculiarities of low-temperature heat capacity of the KCl crystals containing randomly distributed OH- impurities have been studied using pulsed differential calorimetry. The contribution of the two level systems (TLS) and resonance modes to heat capacity was observed. At low concentration (the...

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Veröffentlicht in:Journal of low temperature physics 2003-03, Vol.130 (5-6), p.529-542
Hauptverfasser: NADAREISHVILI, M. M, KVAVADZE, K. A, BASILIA, G. G, DVALI, Sh. V, KHORGUASHVILI, Z
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Sprache:eng
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Zusammenfassung:The peculiarities of low-temperature heat capacity of the KCl crystals containing randomly distributed OH- impurities have been studied using pulsed differential calorimetry. The contribution of the two level systems (TLS) and resonance modes to heat capacity was observed. At low concentration (the case of isolated-not interacted impurities) the experimental data are in agreement with the theory. At high concentrations (the case of interacting impurities) an excess low-temperature specific heat was observed attributed by us to the creation of the wide spectrum of force constants due to chaotic distribution of interacting impurities (observed effect is similar to the well-known one in amorphous solids induced by so-called 'Boson Peak,' but it cannot be explained by soft potential model). At the same time the part of hydroxyl taking place in resonance oscillations decreases with the increase of concentration. The results of these experiments explain also the anomaly observed earlier in KCl:OH systems (De Yoreo et al.) that was attributed to unknown impurities.
ISSN:0022-2291
1573-7357
DOI:10.1023/A:1022487920082