Measuring heat capacity at extremely low temperatures is very important for detecting phase transitions and low energy excitations from the ground states. By these measurements, one can clearly the phase relations of various electronic phases related to the spin, charge, lattice, and other degrees of freedom. We are constructing a low temperature calorimeter on the dilution refrigerator at Institute of Molecular Science (IMS) to attain low temperature measurements down to 50 mK. The main idea of the sample cell has already been reported. We have constructed a small size thermally relaxation cell consisting of thermometry chip and film type strain gauge heater. The heat link from the mixing chamber to the sample stage was adjusted to attain better control of the sample stage in a wide temperature region. The calorimetry cell is available for the thermodynamic measurements for organic conductors and organic magnets.
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Fig. 1. A schematic view of the dilution refrigerator (Kelvinox system) at Institute for Molecular Science. The cooling power of the refrigerator was confirmed as 300 μW at 100 mK and the minimum temperature attained was 21 mK without sample stage. |
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Photo 1. Pictures of (a) the gas handling system and (b) the top flange of the Kelvinox dilution system. |