Identification of novel compositions of ferromagnetic shape-memory alloys using composition spreads.
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.
Takeuchi
I
I
Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA. takeuchi@squid.umd.edu
Famodu
O O
OO
Read
J C
JC
Aronova
M A
MA
Chang
K-S
KS
Craciunescu
C
C
Lofland
S E
SE
Wuttig
M
M
Wellstood
F C
FC
Knauss
L
L
Orozco
A
A
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
D000497:Alloys; D003722:Dental Alloys; C093824:Martensite; D008345:Manganese; D009532:Nickel; D005708:Gallium; D007501:Iron