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 9T 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 magneto-caloric 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.