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TT: Fachverband Tiefe Temperaturen

TT 22: Superconductivity – Poster I

TT 22.34: Poster

Montag, 9. März 2026, 18:00–20:00, P1

Fast calibration and performance verification of RuO₂ chip thermometers down to 20 mK utilizing adiabatic demagnetization refrigeration in the PPMS. — •Jorginho Villar Guerrero, Philipp Gegenwart, Christian Heil, and Tim Treu — University Augsburg

Access to temperatures in the millikelvin (mK) range is essential for the research and development of quantum technologies. Calibrated low-temperature sensors are expensive and only available with long lead times. We focus on the fast calibration of cheap Ruthenium Oxide (RuO₂) thick-film resistor chips that are widely used in the automotive industry and are therefore readily available. Upon cooling to below 4 K, they show a pronounced rise of the resistance, which follows variable-range hopping and can be used for low-temperature thermometry down to 20 mK [1]. The thermometers feature a low mass and consequently a low specific heat. Their small size allows mounting them on small contact surfaces. For calibration and performance tests down to mK temperatures, we utilize adiabatic demagnetization of frustrated oxide quantum magnets in the Quantum Design Physical Property Measurement System [2]. We present a miniaturized thermometer calibration setup with reduced response time and minimal self-heating for use down to 20 mK. We report measurements against secondary thermometers with traceable calibration as well as verification with superconducting transitions of Rh-Ir alloy.
[1] R. W. Willekers et al., Cryogenics 30, Issue 4, 1990
[2] T. Treu et al., J. Phys. Condens. Matter 37, 013001 (2025)

Keywords: Thermometer; Magnet refrigeration; Adiabatic demagnetisation refrigeration; Low temperatur; Frustrated oxide quantum magnets