Achievement of table-like magnetocaloric effect and enhanced refrigerant capacity in the dual-phase Ho5Pd2/Ho3Pd2 composite

Realization of table-like magnetocaloric effect (MCE) is one of the important requirements to achieve high efficiency for magnetic refrigeration that uses the Ericsson cycle. In this work, optimal weight fraction x in (Ho ₅Pd ₂) _x(Ho ₃Pd ₂) _1-x to achieve table-like MCE was established by calculating method based on the Ho-Pd binary phase diagram and the MCEs of the individual Ho ₅Pd ₂ and Ho ₃Pd ₂ phases. Dual-phase composites (Ho ₅Pd ₂) _x(Ho ₃Pd ₂) _1-x ( x=0.525, 0.55, 0.575, 0.6) were prepared by arc melting and annealing. All the (Ho ₅Pd ₂) _x(Ho ₃Pd ₂) _1-x alloys crystallize in the phases of Ho ₅Pd ₂ and Ho ₃Pd ₂, in which the table-like MCEs were obtained. Especially, a table-like MCE with a temperature span of 20 K is observed in the (Ho ₅Pd ₂) _0.6(Ho ₃Pd ₂) _0.4 composite for a field change of 0–5 T. The corresponding maximum magnetic entropy change ( − ▵ S M max ⁡ ), refrigerant capacity (RC) and temperature-averaged entropy change (TEC) are determined to be 10.6 J/kg K, 428.7 J/kg and 10.5 J/kg K (∆H=20 K), respectively. The value of RC is enhanced by 13 % compared with those in the single Ho ₅Pd ₂ (382.3 J/kg) and Ho ₃Pd ₂ (301.5 J/kg). The considerable RC and TEC values together with the table-like feature MCE suggest that the (Ho ₅Pd ₂) _x(Ho ₃Pd ₂) _1-x composite materials meet the requirements of low temperature magnetic refrigeration based on the Ericsson-cycle.