Giant magnetocaloric effect from reverse martensitic transformation in Ni-Mn-Ga-Cu ferromagnetic shape memory alloys

JOURNAL OF ALLOYS AND COMPOUNDS

卷:670

Article

Sarkar, Sudip Kumar¹  Sarita¹  Babu, P. D.²  Biswas, Aniruddha¹  Siruguri, Vasudeva²  Krishnan, Madangopal¹ 

[1] Bhabha Atom Res Ctr, Glass & Adv Mat Div, Bombay 400085, Maharashtra, India

[2] BARC, Mumbai Ctr, UGC DAE Consortium Sci Res, Bombay 400085, Maharashtra, India

关键词: FSMA;    Martensitic transformation;    Magnetocaloric effect;    NiMnGaCu;   

DOI  :  10.1016/j.jallcom.2016.02.039

来源: Elsevier

【 摘 要 】

In an effort to produce Giant Magnetocaloric effect (GMCE) near room temperature, in a first ever such study, the austenite transformation temperature (A(s)) was fine tuned to ferromagnetic Curie temperature (T-C) in Ferromagnetic Shape Memory Alloys (FSMA) and a large GMCE of Delta SM = -81.8 J/Kg-K was achieved in Ni50Mn18.5Cu6.5Ga25 alloy during reverse martensitic transformation (heating cycle) for a magnetic field change of 9 T at 303 K. Fine tuning of A(s) with T-C was achieved by Cu substitution in Ni50Mn25-xCuxGa25 (0 <= x <= 7.0)-based FSMAs. Characterizations of these alloys were carried out using Optical and Scanning Electron Microscopy, X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC) and DC magnetization measurements. Addition of Cu to stoichiometric Heusler type Ni2MnGa increases the martensitic transformation temperatures and decreases T-C. Concurrently, Delta SM increases with Cu addition and peaks at 6.5 at% Cu for which there is a virtual overlap between T-C and A(s). Maximum Refrigerant Capacity (RCP) of 327.0 J/Kg was also achieved in the heating cycle for 9 T field change at 303 K. Corresponding values for the cooling cycle measurements (measured during forward transformation) were 30.4 J/Kg-K and 123.5 J/Kg respectively for the same 6.5 at% Cu sample under the same thermo-magnetic conditions. (C) 2016 Elsevier B.V. All rights reserved.

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