Abstract
In this paper, the hyperkagome lattice of Gd spins in a garnet compound, Gd3CrGa4O12, is studied using bulk measurements and density functional computations, and the observation of large magnetocaloric effect corresponding to an entropy change, ΔSm = 45 J kg-1K-1 (≈ 45 J mol-1K-1) at 2 K, 8 T is reported. Though the compound defies long-range magnetic order down to 0.4 K, a broad feature below 10 K is observed in the specific heat with two low temperature anomalies at T∗ ≈ 0.7 K and TS ≈ 2.45 K. The anomaly at T∗ is reminiscent of one in Gd3Ga5O12, where it is related to the development of a complex magnetic phase, whereas the TS-peak is accounted for by a multilevel Schottky-like model. The spin-lattice relaxation times studied by nuclear magnetic resonance experiments show that the relaxation is dominated by the magnetic fluctuations in Cr which has a longer relaxation time compared to that of the garnet, Lu3CrGa4O12 containing a nonmagnetic rare earth. Our first-principles density functional theory calculations agree well with the experimental results and support short-range magnetic order in the Gd-sublattice and antiferromagnetism in the Cr-sublattice. The importance of spin fluctuations and short-range order in the rare earth and transition metal lattices in garnets resulting in large magnetocaloric effect is brought out through this work.
| Original language | English |
|---|---|
| Pages (from-to) | 15144-15153 |
| Number of pages | 10 |
| Journal | Inorganic Chemistry |
| Volume | 59 |
| Issue number | 20 |
| DOIs | |
| State | Published - Oct 19 2020 |
Funding
H.S.N acknowledges the faculty start-up funds and the University Research Initiative (URI) from UTEP. X-ray Core Facility at UTEP is thanked for the support. N.B. acknowledge the support of project CeNIKS cofinanced by the Croatian Government and the European Union through the European Regional Development Fund – Competitiveness and Cohesion Operational Programme (Grant No. KK.01.1.1.02.0013). Part of this work is financed within the Croatian-Swiss Research Program of the Croatian Science Foundation and the Swiss National Science Foundation with funds obtained from the Swiss-Croatian Cooperation Programme. This work used the Extreme Science and Engineering Discovery Environment (XSEDE) resource Stampede2 at TACC through allocation TG-DMR110093. K.G. acknowledges support from the US DOE’s Early Career Research Program. N.P. acknowledges support from INL’s LDRD program (18P37-008FP). Work at Texas A&M was supported by the Robert A. Welch Foundation, Grant No. A-1526.