Title :
Magnetic properties, structure and shape-memory transitions in Ni-Mn-Ga thin films grown by ion-beam sputtering
Author :
Ahn, Jae-Pyoung ; Cheng, Ning ; Lograsso, Thomas ; Krishnan, Kannan M.
Author_Institution :
Ceramic Process. Res. Center, Korea Adv. Inst. of Sci. & Technol., Seoul, South Korea
fDate :
7/1/2001 12:00:00 AM
Abstract :
Ni1-2xMnxGax (x~0.2 and 0.25) alloys in thin film form were prepared by ion-beam sputtering from alloy targets. For Si(001) substrates the structure/texture of the films are a function of the growth temperature (Tg). The tetragonal martensite structure with a (220) texture was obtained for an optimal T g~300-350°C. At higher temperatures a cubic silicide (Mn 12Ni4Si3) was obtained. At room temperature, optimal films with the stoichiometric composition (x ~ 0.2) showed a ferromagnetic hysteresis behavior characterized by significant in-plane rotation. The coercivity of the films was 310 Oe and temperature-dependent measurements confirmed a Curie temperature, Tc~340 K. At room temperature the films show a modulated 7M martensite structure which was observed in in situ heating experiments to transforms to the cubic austenite phase at 500°C
Keywords :
Curie temperature; coercive force; gallium alloys; magnetic hysteresis; magnetic thin films; manganese alloys; nickel alloys; shape memory effects; sputter deposition; texture; 293 to 298 K; Curie temperature; NiMnGa; Si; Si(001) substrates; coercivity; cubic austenite phase; cubic silicide; ferromagnetic hysteresis; growth temperature; in-plane rotation; ion-beam sputtering; modulated 7M martensite structure; shape-memory transitions; temperature-dependence; tetragonal martensite structure; texture; thin films; Gallium alloys; Magnetic films; Magnetic hysteresis; Magnetic properties; Manganese alloys; Nickel alloys; Silicides; Sputtering; Substrates; Temperature;
Journal_Title :
Magnetics, IEEE Transactions on
