Room-temperature magnetocaloric effect of Ni–Co–Mn–Al Heusler alloys

Abstract Magnetocaloric effect of the Ni–Co–Mn–Al quaternary alloys was evaluated with the aim of fine-tuning the composition such that the temperature at which the maximum entropy change (|Δ S M | pk ) occurs coincided with room temperature. Out of the three alloys tested (Ni 41.5 Co 8.5 Mn 32 Al 18 , Ni 41 Co 9 Mn 32.5 Al 17.5 and Ni 41 Co 9 Mn 32 Al 18 ), Ni 41 Co 9 Mn 32 Al 18 was optimal with |Δ S M | pk of 2.1 J kg −1  K −1 at 10 kOe observed at 300 K as designed and the refrigeration capacity (RC) was 52 J kg −1 . Both values do compare favorably with other Heusler-type alloys, considering the relatively low material cost of the Ni–Mn–Al alloy. In addition, Ni 41.5 Co 8.5 Mn 32 Al 18 and Ni 41 Co 9 Mn 32 Al 18 alloys were chemically joined (using an epoxy) to attain |Δ S M | pk and RC values that nearly corresponded to the average values of the original alloys, providing a method for further tailoring the magnetic properties of the refrigerant in addition to the refinement of the composition.