AC-Calorimetry at High Pressure and Low Temperature

TL;DR

This paper discusses recent advancements in AC-calorimetry techniques for high-pressure, low-temperature experiments, enabling semi-quantitative specific heat measurements up to 10 GPa and below 1 K.

Contribution

It introduces adapted AC-calorimetry methods for high-pressure environments using different pressure media and demonstrates measurement capabilities below 1 K and above 10 GPa.

Findings

Pressure transmitting media affect measurement frequency range.

Solid He allows higher cut-off frequency than steatite.

Pressure dependence of specific heat coefficient aligns with resistivity data.

Abstract

Recent developments of the AC-calorimetric technique adapted for the needs of high pressure experiments are discussed. A semi-quantitative measurement of the specific heat with a Bridgman-type of pressure cell as well as a diamond anvil cell is possible in the temperature range 0.1 K < T < 10 K. The pressure transmitting medium used to ensure good pressure conditions determines to a great extent via its thermal conductivity the operating frequency and thus the accessible temperature range. Investigations with different pressure transmitting media for T > 1.5 K reveal for solid He a cut-off frequency which is considerably higher than for steatite. Experiments below 1 K and pressures above 10 GPa clearly show that the pressure dependence of the linear temperature coefficient of the specific heat can be measured. It is in qualitative agreement to a related quantity obtained quasi-simultaneously by electrical resistivity measurements on the same sample.