Identification of novel compositions of ferromagnetic shape-memory alloys using composition spreads

• Published in: Nature materials Vol. 2; no. 3; pp. 180 - 184
• Main Authors: Takeuchi, I, Famodu, O.O, Read, J.C, Aronova, M.A, Chang, K.-S, Craciunescu, C, Lofland, S.E, Wuttig, M, Wellstood, F.C, Knauss, L, Orozco, A
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.03.2003
• Subjects: Alloys - analysis; Crystallography, X-Ray; Dental Alloys - chemistry; Gallium - chemistry; Inspection; Iron - chemistry; Magnetics; Magnetism; Manganese - chemistry; Microscopy; Nickel - chemistry; Phase transitions; Physics; Temperature; Thin films; Transition temperatures; United States > US; Maryland
• ISSN: 1476-1122; 1476-4660
• DOI: 10.1038/nmat829

Exploration of new ferroic (ferroelectric, ferromagnetic or ferroelastic) materials continues to be a central theme in condensed matter physics and to drive advances in key areas of technology. Here, using thin-film composition spreads, we have mapped the functional phase diagram of the Ni-Mn-Ga system whose Heusler composition Ni(2)MnGa is a well known ferromagnetic shape-memory alloy. A characterization technique that allows detection of martensitic transitions by visual inspection was combined with quantitative magnetization mapping using scanning SQUID (superconducting quantum interference device) microscopy. We find that a large, previously unexplored region outside the Heusler composition contains reversible martensites that are also ferromagnetic. A clear relationship between magnetization and the martensitic transition temperature is observed, revealing a strong thermodynamical coupling between magnetism and martensitic instability across a large fraction of the phase diagram.