title: Identification of novel compositions of ferromagnetic shape-memory alloys using composition spreads.
abstract: 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.
authors.affiliation: Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA. takeuchi@squid.umd.edu
authors.forename: I
authors.initials: I
authors.lastname: Takeuchi
authors.forename: O O
authors.initials: OO
authors.lastname: Famodu
authors.forename: J C
authors.initials: JC
authors.lastname: Read
authors.forename: M A
authors.initials: MA
authors.lastname: Aronova
authors.forename: K-S
authors.initials: KS
authors.lastname: Chang
authors.forename: C
authors.initials: C
authors.lastname: Craciunescu
authors.forename: S E
authors.initials: SE
authors.lastname: Lofland
authors.forename: M
authors.initials: M
authors.lastname: Wuttig
authors.forename: F C
authors.initials: FC
authors.lastname: Wellstood
authors.forename: L
authors.initials: L
authors.lastname: Knauss
authors.forename: A
authors.initials: A
authors.lastname: Orozco
mesh_terms: D000497:Alloys / Q000032:analysis*; D018360:Crystallography, X-Ray; D003722:Dental Alloys / Q000737:chemistry; D005708:Gallium / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D008280:Magnetics; D008345:Manganese / Q000737:chemistry; D009532:Nickel / Q000737:chemistry; D013696:Temperature
chemical_list: D000497:Alloys; D003722:Dental Alloys; C093824:Martensite; D008345:Manganese; D009532:Nickel; D005708:Gallium; D007501:Iron