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Enhanced cryogenic magnetocaloric effect in Eu8Ga16Ge30 clathrate nanocrystals

TitleEnhanced cryogenic magnetocaloric effect in Eu8Ga16Ge30 clathrate nanocrystals
Publication TypeJournal Article
Year of Publication2015
AuthorsBiswas, A, Chandra, S, Stefanoski, S, Blazquez, JS, Ipus, JJ, Conde, A, Phan, MH, Franco, V, Nolas, GS, Srikanth, H
JournalJournal of Applied Physics
Date Published01
Type of ArticleArticle
ISBN Number0021-8979
Accession NumberWOS:000348356600010
Keywordsnanoparticles, surface spin disorder, thermoelectric applications

20 K) in Eu8Ga16Ge30 clathrate (type-I) nanocrystals prepared by a ball milling method. With reduction in the crystal size to 15 nm, -Delta S-M is enhanced at low temperatures, reaching the highest value (similar to 10 J/kg K) at 5K for a field change of 5 T. For all samples investigated, there is a cross-over temperature (similar to 25 K) in -Delta S-M (T) above which -Delta S-M decreases with crystal size, opposite to that observed at low temperatures. A careful analysis of the magnetic and magnetocaloric data reveals that as the crystal size decreases the magnetic interaction between Eu2+ ions on the Eu2 site governing the primary ferromagnetic transition at similar to 35K becomes gradually weaker, in effect, altering the interaction between Eu2+ ions occupying the Eu1 and Eu2 sites responsible for the secondary ferromagnetic transition at 15 K. As a result, we have observed a strong change in magnetization and the enhancement of -Delta S-M at low temperature. (C) 2015 AIP Publishing LLC.

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