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Magnetocaloric Effect in a Frustrated Gd-Garnet with No Long-Range Magnetic Order
Naveen Kumar Chogondahalli Muniraju1, Raju Baral2, Yefan Tian3
1Institut für Festkörperphysik, TU Wien, Wiedner Hauptstr. 8-10/138, 1040 Wien, Austria.
Inorganic Chemistry
|October 6, 2020
Summary
Researchers studied Gd3CrGa4O12, finding a large magnetocaloric effect of 45 J kg-1K-1 at 2 K. This magnetic garnet shows short-range order and spin fluctuations, crucial for its cooling properties.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Magnetism
Background:
- Garnet compounds with rare-earth elements are of interest for magnetic properties.
- Understanding magnetic interactions in complex lattices is crucial for materials development.
Purpose of the Study:
- To investigate the magnetic properties of the hyperkagome lattice in Gd3CrGa4O12.
- To report the observation of a large magnetocaloric effect.
- To elucidate the relationship between magnetic order, spin fluctuations, and magnetocaloric properties.
Main Methods:
- Bulk measurements (specific heat, magnetic susceptibility).
- Nuclear magnetic resonance (NMR) experiments to study spin-lattice relaxation times.
- First-principles density functional theory (DFT) calculations.
Main Results:
- Observed a large magnetocaloric effect with an entropy change of 45 J kg-1K-1 at 2 K and 8 T.
- The compound lacks long-range magnetic order down to 0.4 K but exhibits magnetic anomalies below 10 K.
- DFT calculations support short-range magnetic order in the Gd-sublattice and antiferromagnetism in the Cr-sublattice.
- Spin-lattice relaxation is dominated by magnetic fluctuations in Cr.
Conclusions:
- Short-range magnetic order and spin fluctuations in both rare-earth and transition-metal sublattices are key to the large magnetocaloric effect in this garnet.
- The study highlights the importance of these factors for designing advanced magnetic refrigerants.
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