Field-induced structural transition and the related magnetic entropy change in Ni43Mn43Co3Sn11 alloy

Magnetic properties and magnetic entropy change ΔS were investigated in Heusler alloy Ni43Mn43Co3Sn11. With decreasing temperature this alloy undergoes a martensitic structural transition at TM=188 K. The incorporation of Co atoms enhances ferromagnetic exchange for parent phases. Austenitic phase with cubic structure shows strong ferromagnetic behaviors with Curie temperature TCA at 346 K, while martensitic phase shows weak ferromagnetic properties. An external magnetic field can shift TM to a lower temperature at a rate of 4.4 K/T, and a field-induced structural transition from martensitic to austenitic state takes place at temperatures near but below TM. As a result, a great magnetic entropy change with positive sign appears. The size of ΔS reaches 33 J/kg K under 5 T magnetic field. More important is that the ΔS displays a table-like peak under 5 T, which is favorable for Ericsson-type refrigerators.