Decoupling of Gd-Cr magnetism and giant magnetocaloric effect in layered honeycomb tellurate GdCrTeO_6

摘要

We report the decoupling of Gd-Cr magnetism and the resulting giant magnetocaloric effect in honeycomb-lattice tellurate GdCrTeO_6. This compound adopts the hexagonal structure with the space group P-3. The susceptibility curve presents a paramagnetic behavior from room temperature to 2 K. Very intriguingly, however, the heat capacity measurement probes a λ-like peak at T_N = 10 K, characterizing the long-range antiferromagnetic order. This suggests that the Gd and Cr sublattices are magnetically independent, i.e., the Gd ions are paramagnetic and the strong paramagnetism nearly masks the antiferromagnetic order of Cr ions, which is further evidenced by our ESR data. The maximum magnetic entropy change at 2 K is 41.8 J kg~(-1) K~(-1) in a field range of 0-7 T and 30.3 J kg~(-1) K~(-1) for 0-3 T, larger than those of most of the Gd oxides reported. The observed giant magnetocaloric effect is due to strong paramagnetism of Gd ions.