Metastability of ferromagnetic Ni-Mn-Sn Heusler alloys

TitleMetastability of ferromagnetic Ni-Mn-Sn Heusler alloys
Publication TypeJournal Article
Year of Publication2010
AuthorsYuhasz WM, Schlagel DL, Xing Q, McCallum RW, Lograsso TA
Journal TitleJournal of Alloys and Compounds
Date Published03/04
ISBN Number0925-8388
Accession NumberISI:000276018900144
Keywordsannealing, GA, Heusler alloy, magnetic-properties, magnetization, magnetocaloric, Ni-Mn-Sn alloy, phase decomposition, PHASE-TRANSFORMATION, shape-memory alloys

We previously showed that extended 4-week anneals at 1223 K were required to achieve structural and chemical homogeneity in the off-stoichiometric Ni-Mn-Sn Heusler alloy solid solution. To insure that the transition from the high temperature B2 to the room temperature L2(1) phase was complete, we performed low temperature (773 K) anneals, similar to 150 K below the reported B2 -> L2(1) transition temperature, on the 1223 K homogenized samples. Drastic changes in the magnetization measurements of the annealed samples suggested that the intermediate compositions of the L2(1) phase were metastable. TEM and XRD analyses confirmed the decomposition of the single-phase Heusler alloys into two phases with compositions close to Ni54Mn45Sn1 and Ni50Mn35Sn20. The observed phase decomposition indicated that the off-stoichiometric Ni-Mn-Sn Heusler alloys, that feature martensitic transformations, are metastable at 773 K. (c) 2009 Elsevier B.V. All rights reserved.

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