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

Magnetic properties and magnetic entropy change DS were investigated in Heusler alloy Ni43Mn43Co3Sn11. With decreasing temperature this alloy undergoes a martensitic structural transition at T-M = 188K. The incorporation of Co atoms enhances ferromagnetic exchange for parent phases. Austenitic phase with cubic structure shows strong ferromagnetic behaviors with Curie temperature T-C(A) at 346 K, while martensitic phase shows weak ferromagnetic properties. An external magnetic field can shift T-M 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 T-M. As a result, a great magnetic entropy change with positive sign appears. The size of Delta S reaches 33 J/kg K under 5T magnetic field. More important is that the Delta S displays a table-like peak under 5T, which is favorable for Ericsson-type refrigerators. (C) 2009 Elsevier B. V. All rights reserved.