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

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 (|ΔSM|pk) occurs coincided with room temperature. Out of the three alloys tested (Ni41.5Co8.5Mn32Al18, Ni41Co9Mn32.5Al17.5 and Ni41Co9Mn32Al18), Ni41Co9Mn32Al18 was optimal with |ΔSM|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, Ni41.5Co8.5Mn32Al18 and Ni41Co9Mn32Al18 alloys were chemically joined (using an epoxy) to attain |ΔSM|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.