ISSN:
1573-7357
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract The natural minerals calcite, magnesite, and dolomite containing ∼0.1% Mn 2+ ions have been investigated to determine their usefulness as cooling agents for adiabatic demagnetization. Cooling curves below 1°K, obtained by a series of adiabatic demagnetizations, gave characteristic temperatures: ∼0.05°K for the pink and the white calcites and the magnesite, and ∼0.1°K for the dolomite, in fair agreement with the values predictable from the ESR data for Mn 2+ . As for the specific heat constant,cT 2/R, the agreement with the ESR was good below 0.4° K with values of 6×10 −3 (°K) 2 for the pink and the white calcites and the magnesite, and 22×10 −3 (°K) 2 for the dolomite. The static magnetic susceptibility was measured from 4.2 to 0.06° K and gave the values of Curie constant: 0.44×10 −3 , 0.27×10 −3 , and 0.05×10 −3 emu/cm 3 at high temperature, for the polycrystalline samples of pink calcite, magnesite, and dolomite, respectively. The pink calcite and the dolomite obey Curie's law down to ∼0.8°K and the magnesite to ∼0.3°K. The ordering temperatures for these samples are deduced to be lower than 0.06°K. Measurement of the thermal conductivityK(T) is reported for several types of samples between 4 and 0.2°K.K(T) of the Iceland spar is ∼15 times better than that of CrK alum as reported elsewhere, whereas that of the single crystal of white calcite is about two times higher. The polycrystalline samples are poor from this point of view.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00628212
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