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

Abstract

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 (ΔSM) 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 (ΔSMpk) 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 ΔSMpk and the average magnetic moment per transition metal atom (⟨μ⟩Fe,Mn) has been presented.