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Free-spin dominated magnetocaloric effect in dense Gd3+double perovskites

DOI: 10.1021/acs.chemmater.2c00261 DOI Help

Authors: Eliseanne C. Koskelo (University of Cambridge) , Cheng Liu (University of Cambridge) , Paromita Mukherjee (University of Cambridge) , Nicola D. Kelly (University of Cambridge) , Sian E. Dutton (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials

State: Published (Approved)
Published: March 2022
Diamond Proposal Number(s): 28349

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 analogue 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.

Journal Keywords: Entropy; Ions; Magnetic properties; Quantum mechanics; Materials

Subject Areas: Materials, Chemistry, Physics

Instruments: I11-High Resolution Powder Diffraction

Added On: 31/03/2022 14:26

Discipline Tags:

Physics Physical Chemistry Chemistry Magnetism Materials Science Chemical Engineering Engineering & Technology Inorganic Chemistry Perovskites Metallurgy

Technical Tags:

Diffraction X-ray Powder Diffraction