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 13.5: Hauptvortrag
Dienstag, 28. März 2023, 11:45–12:15, HSZ 03
Frustrated dipolar materials for low-temperature magnetic refrigeration — •Mike Zhitomirsky — Institute of Interdisciplinary Research, CEA-Grenoble, France
Low-temperature refrigeration is crucial for emergent quantum-information technologies and other scientific applications that outstretch from space telescopes to medicine. This growing demand fuels an interest in alternative low-temperature techniques including the adiabatic demagnetization refrigeration. The existing ADR technologies for the sub-Kelvin range utilize dilute paramagnetic salts of Cr and Fe magnetic ions, which have limited efficiency at higher temperatures. I shall discuss general directions of the ongoing search of prospective refrigerant materials by exploring collective effects in systems of interacting magnetic moments as opposed to noninteracting moments in paramagnetic salts. Specifically, I focus on geometrically frustrated magnets with a residual ground-state degeneracy as well as on dipolar magnets. I present new experimental and theoretical results obtained recently in Grenoble for two dipolar materials: Yb3Ga5O12, which is a spin-1/2 dipolar ferromagnet on a hyper-Kagome lattice, and GdLiF4, which exhibits a hidden magnetic frustration. The striking properties of the latter material including a fractional magnetization plateau demonstrate importance of new magnetocaloric materials not only for applied but also for basic research in magnetism.