Large magnetic entropy change in weberite-type oxides Gd3MO7 (M = Nb, Sb, and Ta)

In the present work, the structure, magnetic properties, and cryogenic magnetocaloric effect of weberite-type oxides Gd3MO7 (M = Nb, Sb, and Ta) are reported through powder X-ray diffraction, bulk susceptibility, and heat capacity measurements, as well as scaling law analysis and a mean-field approach. A remarkably large isothermal magnetic entropy change of 354.0 mJ K−1 cm−3 is observed for Gd3SbO7 under an external field of 9 T at 2.0 K. The relative cooling power is estimated to be 618.9 J kg−1 (4.8 J cm−3) for an applied field of 8.9 T, with the largest adiabatic temperature change being 22.4 K at 6.3 K. The magnetocaloric performance of these oxides is quite impressive when compared with the benchmark magnetic refrigerant, gadolinium gallium garnet (Gd3Ga5O12, GGG). Therefore, Gd3MO7 (M = Nb, Sb, and Ta) are promising alternatives for cryogenic cooling techniques, especially for the magnetic liquefaction of helium.