Abstract
A heat-capacity measurement system has been developed to establish a reliable calorimetric study under magnetic fields. The system is based on the thermal relaxation method by use of a temperature-difference detection system, which incorporates a pair of small thin film resistance thermometers, PTF-7 and is little affected by magnetic fields. Its performance under magnetic fields has been studied by use of a reference sample, whose heat capacity is independent of magnetic fields. SRM 720 provided by NIST, which is made of synthesized sapphire, was selected for this purpose. As this material is non-magnetic insulator, its heat capacity is expected to have small field dependence. The performance of the total system has been studied between 40 and 90K under magnetic fields of up to 7T. The resolution of the system was estimated to be about 2% and independent of the magnitude of magnetic fields. The measured heat capacities under magnetic fields of 0T, 5T and 7T agreed with each other within the resolution of the measurement.
