engleski

Magnetocaloric Effect in a Frustrated Gd-Garnet with No Long-Range Magnetic Order

In this paper, the hyperkagome lattice of Gd spins in agarnet compound, Gd3CrGa4O12, is studied using bulk measurementsand density functional computations, and the observation of largemagnetocaloric effect corresponding to an entropy change, ΔSm=45Jkg−1K−1(≈45 J mol−1K−1) at 2 K, 8 T is reported. Though thecompound defies long-range magnetic order down to 0.4 K, a broadfeature below 10 K is observed in the specific heat with two lowtemperature anomalies atT*≈0.7 K andTS≈2.45 K. The anomaly atT*is reminiscent of one in Gd3Ga5O12, where it is related to thedevelopment of a complex magnetic phase, whereas theTS-peak isaccounted for by a multilevel Schottky-like model. The spin−latticerelaxation times studied by nuclear magnetic resonance experimentsshow that the relaxation is dominated by the magneticfluctuations in Crwhich has a longer relaxation time compared to that of the garnet, Lu3CrGa4O12containing a nonmagnetic rare earth. Ourfirst-principles density functional theory calculations agree well with the experimental results and support short-range magnetic order inthe Gd-sublattice and antiferromagnetism in the Cr-sublattice. The importance of spinfluctuations and short-range order in the rareearth and transition metal lattices in garnets resulting in large magnetocaloric effect is brought out through this work.

garnet compound, Frustration

nije evidentirano