Free-spin dominated magnetocaloric effect in dense Gd3+ double perovskites
Journal Title
Chemistry of Materials
ISSN
0897-4756
Publisher
American Chemical Society
Type
Article
This Version
AM
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Dutton, S., Koskelo, E., Liu, C., Mukherjee, P., & Kelly, N. Free-spin dominated magnetocaloric effect in dense Gd3+ double perovskites. Chemistry of Materials https://doi.org/10.17863/CAM.82511
Abstract
Frustrated lanthanide oxides with dense magnetic lattices are of fundamental interest for their potential in cryogenic refrigeration due to
a large ground state entropy and suppressed ordering temperatures, but can often be limited by short-range correlations. Here, we present examples of frustrated fcc oxides, Ba2GdSbO6 and Sr2GdSbO6 and the new site-disordered analog Ca2GdSbO6 ([CaGd]A[CaSb]BO6), in which the magnetocaloric effect is influenced by minimal superexchange (J1 ∼ 10 mK). We report on the crystal structures using powder x-ray diffraction and the bulk magnetic properties through low-field susceptibility and isothermal magnetization measurements. The Gd compounds exhibit a magnetic entropy change of up to -15.8 J/K/molGd in a field of 7 T at 2 K, a 20% excess compared to the value of -13.0 J/K/molGd for a standard in magnetic refrigeration, Gd3Ga5O12. Heat capacity measurements indicate a lack of magnetic ordering down to 0.4 K for Ba2GdSbO6 and Sr2GdSbO6, suggesting cooling down through the liquid 4-He regime. A mean-field model is used to elucidate the role of primarily free spin behavior in the magnetocaloric performance of these compounds in comparison to other top-performing Gd-based oxides. The chemical flexibility of the double perovskites raises the possibility of further enhancement of the magnetocaloric effect in the Gd3+ fcc lattices.
Relationships
Is supplemented by: https://doi.org/10.17863/CAM.82520
Sponsorship
Winton Programme for the Physics of Sustainability.
Churchill Scholarship from the Winston Churchill Foundation of the United States.
EPSRC EP/R513180/1, EP/M0005/24/1.
Diamond Light Source for time on I11 under BAG proposal CY28349
Funder references
EPSRC (EP/T028580/1)
Embargo Lift Date
2025-03-16
Identifiers
This record's DOI: https://doi.org/10.17863/CAM.82511
This record's URL: https://www.repository.cam.ac.uk/handle/1810/335071
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