Thermomagnetic properties of very heavy fermions suitable for adiabatic demagnetisation refrigeration at low temperature

ABSTRACT

With the aim to improve the performance of classical paramagnetic salts for adiabatic refrigeration processes at the sub-Kelvin range, relevant thermodynamic parameters of some new Yb-based intermetallic compounds are analysed and compared. Two main applications are considered: (i) those requiring temperature fixed-points to be reached applying magnetic fields of moderate intensity for satellite applications, and (ii) those which can be used for controlled thermal drifts in laboratory applications. Different thermomagnetic trajectories of the entropy are identified depending on respective specific heat behaviours and the constraints imposed by the Nernst postulate at the sub-Kelvin range. Some simple relationships are proposed to compare the diverse magnetocaloric characteristics of different systems. This procedure allows to include the classical Cerium-Magnesium-Nitride (CMN) salt in that comparison.

KEYWORDS:

• Magnetic refrigeration
• heavy fermions
• entropy
• frustration
• specific heat

Acknowledgments

The author is grateful to M. Giovannini, S. Gabani, M. Reiffers, T. Gruner, E. Bauer, H. Michor and A. Strydom for allowing to access to original experimental results.

Disclosure statement

No potential conflict of interest was reported by the authors.