Relative cooling power enhancement by tuning magneto-structural stability in Ni-Mn-In Heusler alloys

摘要

Off-stoichiometric Ni2MnIn Heusler alloys have drawn recent attention due to their large magnetocaloric entropy change associated with the first-order magneto-structural transition. Here we present crystal structural, calorimetric and magnetic studies of three compositions. Temperature-dependent X-ray diffraction shows clear structural transition from a 6M modulated monoclinic to a L2(1) cubic. A significant enhancement of relative cooling power (RCP) was achieved by tuning the magnetic and structural stability through minor compositional changes, with the measured results quantitatively close to the prediction as a function of the ratio between the martensitic transition (T-m) temperature and austenite Curie temperature (T-C) although the maximal magnetic induced entropy change (Delta S-max) reduction is observed in the same time. The results provided an evaluation guideline of RCPs as well as magnetic-induced entropy change in designing practical active materials. (C) 2018 Published by Elsevier B.V.