SKM 2023 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 13: Focus Session: New Perspectives for Adiabatic Demagnetization Refrigeration in the Kelvin and sub-Kelvin Range (joint session TT/MA)
MA 13.7: Vortrag
Dienstag, 28. März 2023, 12:30–12:45, HSZ 03
ADR below the ordering temperature in triangular KBaGd(BO3)2 — •Noah Winterhalter-Stocker1, Alexander Bellon1, Fabian Hirschberger1, Sebastian Bachus1, Sebastian Erdmann1, Alexander Tsirlin1, 2, Yoshifumi Tokiwa1, 3, Anton Jesche1, and Philipp Gegenwart1 — 1Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, D-86159 Augsburg, Germany — 2Felix Bloch Institute for Solid-State Physics, Leipzig University, D-04103 Leipzig, Germany — 3Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
Compared to the triangular ADR magnet KBaYb(BO3)2 [1] the isotructural sister compound KBaGd(BO3)2 with spin 7/2 moments has a three times enhanced magnetic entropy density of 192 mJK−1cm−3. We report a low-temperature magnetic and thermodynamic investigation of polycrystalline KBaGd(BO3)2 down to 50 mK. Specific heat indicates an antiferromagnetic phase transition at 263 mK, strongly broadened due to randomness and frustration, that becomes suppressed beyond 0.5 T. Further increase of magnetic field shifts the available entropy of Rlog8 towards high temperatures. Interestingly, ADR of a pellet utilizing the same setup as used in [1] reveals a minimal temperature if Tmin=122 mK that is more than twice below TN along with a hold time of more than 8 hours. The combination of minimal temperature and entropy density in KBaGd(BO3)2 is outstanding among known ADR materials.
[1] Y. Tokiwa et al., Communications Materials 2.1, 1-6 (2021)