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, Delta S-M(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 Delta S-M(T) curve with table-like shape, has been found in the temperature interval of 18-44K for the composite with x = 0.4 and for values of the magnetic field change mu(o)Delta H - 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 delta T-FWHM of 32(41) K for mu(o)Delta H 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. (C) 2015 AIP Publishing LLC.