Influence of Mn on the magnetocaloric effect of nanoperm-type alloys

In this paper, the influence of the Mn content on the magnetocaloric response of ribbon-shaped amorphous samples of Fe80−xMnxB20 x=10, 15, 18, 20, and 24 , has been studied. For this purpose, the temperature and field dependence of the magnetic entropy change SM have been obtained from magnetization curves. The partial substitution of Fe by Mn leads to a monotonous change in the Curie temperature TC of the alloys from 438 K for x=10 to 162 K for x=24, in agreement with the coherent-potential approximation. These Curie temperatures could make them good candidates to be used for magnetic refrigeration at room temperature. For an applied field of 1.5 T, the maximum entropy change SM pk passes from 1 J K−1 kg−1 x=10 to 0.5 J K−1 kg−1 x=24 , and the refrigerant capacity varies between 117 J kg−1 x=10 and 68 J kg−1 x=24 . A linear relationship between SM pk and the average magnetic moment per transition metal atom Fe,Mn has been presented. © 2010 American Institute of Physics.