Magnetism and giant magnetocaloric effect in rare-earth-based compounds R_(3)BWO_9(R=Gd,Dy,Ho)

The magnetism and magnetocaloric effect(MCE)of rare-earth-based tungstate compounds R_(3)BWO_9(R=Gd,Dy,Ho)have been studied by magnetic susceptibility,isothermal magnetization,and specific heat measurements.No obvious long-range magnetic ordering can be found down to 2 K.The Curie-Weiss fitting and magnetic susceptibilities under different applied fields reveal the existence of weak short-range antiferromagnetic couplings at low temperature in these systems.The calculations of isothermal magnetization exhibit a giant MCE with the maximum changes of magnetic entropy being 54.80 J/kg-K at 2 K for Gd_(3)BWO_9,28.5 J/kg-K at 6 K for Dy_(3)BWO_(9),and 29.76 J/kg-K at 4 K for Ho_(3)BWO_9,respectively,under a field change of 0-7 T.Especially for Gd_(3)BWO_9,the maximum value of magnetic entropy change(-ΔS_M^(max))and adiabatic temperature change(-ΔT_(ad)^(max))are 36.75 J/kg·K and 5.56 K for a low field change of 0-3 T,indicating a promising application for low temperature magnetic refrigeration.