AC calorimetry system using commercially available microchip device and its application for tiny single crystals of molecule-based compounds

The constructional details and performance of a low-temperature ac calorimetric system for extremely small single crystal samples of molecule-based compounds of which sensing parts is consisting of commercially available micro-chip device of XEN-39390 are reported. We succeeded to detect the thermal anomaly related to the glass formation of the ethylene conformation in a charge transfer complex of κ-(BEDT-TTF)2Cu[N(CN)2]Br, where BEDT-TTF is bisethylenedithiotetrathiafulvalene. From the analyses of temperature and frequency dependences of heat capacity, we suggest that XEN-39390 can give similar experimental resolution as that of TCG-3880 with much smaller single crystals less than 100 ng. We also observed a glass-like freezing of molecular dynamics in the large asymmetric cations in EtMe3Sb[Pd(dmit)2]2 which are known as a spin liquid compound by single piece of crystal where dmit is 1,3-dithiole-2-thione-4,5-dithiolate. The comparison with the relaxation calorimetry result with absolute precision is performed.