Dresden 2020 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 34: Correlated Electrons: f-Electron Systems and Heavy Fermions 1
TT 34.12: Talk
Wednesday, March 18, 2020, 12:30–12:45, HSZ 204
Extremely weak magnetic exchange in metallic 4f-electron system leads to enormous magnetocaloric effect — •Thomas Gruner1, Jiasheng Chen1, Dongjin Jang2, Jacintha Banda3, Christoph Geibel3, Manuel Brando3, and Malte Grosche1 — 1Cavendish Laboratory, University of Cambridge, UK — 2KRISS, Daejeon, Republic of Korea — 3MPI CPfS, Dresden, Germany
Traditional cryogenic demagnetisation refrigerators for the temperature range 40 mK < T < 2 K use hydrated paramagnetic salts as cooling agents. This often imposes significant restrictions on equipment designs due to the weak thermal conductivity and the need for hermetic sealing of these insulating materials. Recently, we showed that certain Yb-based metallic materials provide attractive alternatives [1]. In a search for even more appropriate materials we investigated a number of Heusler- and half-Heusler compounds and studied their structural, magnetic, transport and magnetocaloric properties, enabling us to select a particularly promising Yb system.
Our measured data evidence metallic behaviour, the absence of superconductivity and a stable trivalent Yb3+ state, without any sign of a significant Kondo interaction. This new compound can be easily brought into shape, making the production of powerful cooling pills much simpler compared to commonly used paramagnetic salt or garnet refrigerants. By performing different demagnetisation tests, we demonstrated the feasibility of a simple, economical and durable alternative for traditional cooling devices for temperatures down to 120 mK.
[1] Jang, Gruner et al.; Nature Commun.; 6, 8680 (2015)