Modulated-bath AC calorimetry using modified commercial Peltier-elements

TL;DR

This paper introduces a novel AC microcalorimeter based on a modified Peltier element, enabling precise specific heat measurements of small samples across a wide temperature range and magnetic fields, with minimized background heat capacity.

Contribution

The paper presents a new AC calorimeter design using a modified commercial Peltier element for improved accuracy and reduced background heat capacity in specific heat measurements.

Findings

Successfully measured specific heat of a superconductor in high magnetic fields

Achieved minimal background heat capacity with the new device

Demonstrated effective temperature modulation without DC offsets

Abstract

We developed a new type of AC microcalorimeter based on a modulated-bath technique for measuring the specific heat of small microgram samples in the temperature range from 30-300 K, and tested it in magnetic fields up to 14 T. The device is built from a modified commercial Peltier element. The temperature of its top plate can be modulated periodically by Peltier effect, so that the oscillation is symmetrical about the temperature of the main bath. This avoids the problem of DC offsets which plagues conventional AC calorimeters. The sample is attached to a thin thermocouple cross, acting as a weak thermal link to a platform. The absence of a heater reduces the background heat capacity ('addenda') to a minimum. As an illustrative example of the performance of our device, the specific heat in fields up to 14 T of a small single crystal of the high-temperature superconductor Bi2.12Sr1.71Ca1.22Cu1.95Oy has been determined.