Phase transitions and magnetocaloric effect of Ni1.7Co0.3Mn1+xAl1-x Heusler alloys

Abstract

Structural and magnetic phase transitions of Ni1.7Co0.3Mn1+xAl1-x (x = 0.22-0.3) alloys were characterized to evaluate the magnetocaloric effect (MCE) of the alloys. The Curie temperature remained at similar to 360 K regardless of the composition whereas the Al fraction determined the temperature and extent of the martensitic transition. The alloy with x = 0.26 had the highest peak magnetic entropy change (vertical bar Delta S-M vertical bar(pk)) of 2.1 J kg(-1) K-1 and refrigerant capacity (RC) of 49 J kg(-1) with Delta H = 10 kOe, originating from the martensitic transformation. The vertical bar Delta S-M vertical bar(pk) and RC values were comparable to those of other Ni-Mn-X alloys. The alloy with x = 0.3 may also serve as a magnetic refrigerant near room temperature in spite of its relatively low vertical bar Delta S-M vertical bar(pk) and RC values. Our result suggests that it should be possible to fine-tune the composition of the quaternary NiCoMnAl alloy to attain optimal magnetocaloric effect near room temperature. (c) 2013 Elsevier B.V. All rights reserved.Human Resource Development Project of the Korea Institute of Energy Technology Evaluation and Planning (KETEP)Korea government Ministry of Knowledge Econom