Wide temperature AC-calorimetry equipped in a constant loading cubic-anvil-type pressure apparatus

AC-calorimetry was developed for a cubic-anvil-type pressure apparatus, which can explore the electromagnetic properties of matter over temperatures of 2–300 K and pressures of 0–15 GPa. This method was designed to observe the specific heat of fragile crystals that are difficult to mold into desired forms, such as β-Na0.33V2O5 and BaFe2S3. The calorimeter has two main components: a thermometer and a heater. We employed an AuFe (0.07 mol. %)-Chromel thermocouple and NiCr alloy foil/wire as the thermometer and heater, respectively. Using this calorimetry, we successfully observed the pressure dependencies of several transition temperatures in β-Na0.33V2O5 and the jump in the specific heat (ΔCac/T) at the superconducting transition in Pb-metal when under pressure. Meanwhile, the pressure dependencies of the observed ΔCac/T do not coincide with the literature, which may be attributed to the pressure dependence of the thermoelectric power for the AuFe-Chromel thermocouple at around 5 K.