Abstract
The heat capacity of single-crystal manganous chloride has been measured in constant magnetic fields stabilized at exactly 0, 5000, 7500, 10 000, 18 000, 25 000, and 50 000 G. The measurements which cover the range from 1.3° to 4.2°K, extend the results of Murray who made measurements to 7.25 kilogauss. All of the measurements have been made with the field parallel to the a crystallographic axis (b magnetic axis) as were those of Murray. Except at fields high enough to approach paramagnetic saturation the heat-capacity curves have double maxima, but at about 8000 G the maxima at the lower temperatures are below 1.3°K, the lowest temperature of observation. The heat capacity maxima in zero field were found to be at 1.815° and 1.945°K. The loci of the maxima curve at the higher temperature has temperature increasing with field as found by Murray; however, near 12 kilogauss and 2.03°K, it has been found that a reversal takes place and the field increases as the temperature decreases. The curves for the loci of both sets of maxima evidently approach zero values of dH/dT at 0°K. The heat capacity maxima are not high compared to those of adjacent temperature regions and we do not believe they can be identified as ``transition points'' but rather are merely regions of somewhat accelerated ordering to some ultimate arrangement of magnetic moments, such as the general type suggested by Wilkinson et al. on the basis of neutron diffraction. A rather novel magnetopressure explosion occurred due to a sudden temperature rise accompanying adiabatic magnetization while a crack in a crystal was filled with liquid helium II. Some comments on possible apparatus damage when high fields are applied to enclosures containing both liquid helium and magnetic materials are included. The entropy change in 7740 Pyrex glass has been determined as a function of magnetic field at 1.370° and 4.205°K.
Published Version
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