Magnetic entropy table-like shape in RNi2 composites for cryogenic refrigeration

We have investigated the magnetocaloric (MC) effect in a two-phase composite based on melt-spun ribbons of the intermetallic DyNi2 and TbNi2 Laves phases. The temperature dependence of the isothermal magnetic entropy change, ΔSM(T), has been calculated for the biphasic system x(DyNi2) + y(TbNi2) with 0 < x < 1 (i.e., y = 1 − x). The optimum MC properties, i.e., a ΔSM(T) curve with table-like shape, has been found in the temperature interval of 18–44 K for the composite with x = 0.4 and for values of the magnetic field change μoΔH = 2 and 5 T, in good agreement with the experimental data. The refrigerant capacity, RC, reaches 221(526) J kg−1 with a temperature span δTFWHM of 32(41) K for μoΔH of 2(5) T, thus improving the values obtained for the individual RNi2 ribbons. Our findings constitute a good starting point to stimulate the search for new composites with enhanced MC properties at cryogenic temperatures.