Development of heat capacity measurement system for single crystals of molecule-based compounds

We report on construction of a new low temperature heat capacity measurement system. This system was designed for performing thermodynamic investigation by thermal relaxation technique for small amount of samples at extremely low temperature region between 70 mK and 10 K. Two different calorimetry cells for this system were designed. One is a usual-type calorimetry cell consisting of tiny chip-type thermometer and strain gauge heater. The size of the sample stage has been reduced for measuring small samples. The other is designed for performing heat capacity measurements under magnetic fields of which magnitude and direction are accurately controlled. The calorimetry cells with heat capacity measurement unit can be mounted on a handy top-loading type dilution refrigerator of which outer diameter including the adiabatic space is 27 mm. We discuss basic performance and specification of the constructed cells and low temperature heat capacity data of an organic charge transfer salt obtained by this system.