SKM 2023 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 19: Focus Session: New Perspectives for Adiabatic Demagnetization Refrigeration in the Kelvin and sub-Kelvin Range (joint session TT/MA)

TT 19.2: Hauptvortrag

Dienstag, 28. März 2023, 10:00–10:30, HSZ 03

Triangular rare-earth borates for milli-Kelvin adiabatic demagnetization refrigeration — •Philipp Gegenwart — Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg

Adiabatic demagnetization refrigeration (ADR) is a classical cooling technique with renewed recent attention as alternative to costly and elaborate ³He/⁴He dilution refrigeration. Established water containing ADR salts suffer from chemical instability which requires delicate treatment to avoid degradation and ensure good thermal contact. Water-free KBaYb(BO₃)₂ is an excellent alternative with high entropy density that allows ADR to below 20 mK [1]. Sintered pellets with silver powder admixture to ensure good thermal coupling are easy to manufacture, inexpensive and long-term stable even upon heating up to 700^∘C, enabling also ultra-high vacuum applications. KBaYb(BO₃)₂ belongs to a family of rare-earth-based borates with triangular arrangement of magnetic moments. We discuss the impact of geometrical frustration and structural randomness on its low-temperature properties and demonstrate the enormous tunability of cooling power and operating temperature by chemical substitution.

[1] Y. Tokiwa, S. Bachus, K. Kavita, A. Jesche, A.A. Tsirlin, and P. Gegenwart, Commun. Mater. 2 (2021) 42.