Magnetism and giant magnetocaloric effect in rare-earth-based compounds R₃BWO₉ (R = Gd, Dy, Ho)

The magnetism and magnetocaloric effect (MCE) of rare-earth-based tungstate compounds R_3BWO_9 (R = \rm 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\cdotK at 2 K for Gd_3BWO_9, 28.5 J/kg\cdotK at 6 K for Dy_3BWO_9, and 29.76 J/kg\cdotK at 4 K for Ho_3BWO_9, respectively, under a field change of 0-7 T. Especially for Gd_3BWO_9, the maximum value of magnetic entropy change (-\Delta S_M^\max) and adiabatic temperature change ( - \Delta T_\rm ad^\max) are 36.75 J/kg\cdotK and 5.56 K for a low field change of 0-3 T, indicating a promising application for low temperature magnetic refrigeration.