Topic
Magnetic shape-memory alloy
About: Magnetic shape-memory alloy is a research topic. Over the lifetime, 6160 publications have been published within this topic receiving 132576 citations. The topic is also known as: FSMA & ferromagnetic shape memory alloy.
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17 Jun 2014
TL;DR: In this article, the shape memory effect in ternary shape memory alloys is evaluated by the structural changes in microscopic scale, and it is shown that peak locations and intensities chance with ageing duration in martensitic condition.
Abstract: Shape memory alloys exhibit a peculiar property called shape memory effect based on a first order solid state phase transformation, martensitic transformation which occurs in thermal manner on cooling the materials. Martensitic transformation is evaluated by the structural changes in microscopic scale. Copper-based ternary alloys exhibit shape memory effect in metastable beta phase region. These alloys have bcc-based ordered structures at high temperature, and transform martensiticaly to the long-period layered structures on cooling. The material atoms move cooperatively on {110}-type close packed planes of parent phase by means of a shear-like mechanism, and structural and fundamental properties of these alloys are altered by aging in the martensitic state. Therefore, the ageing gives rise to the structural changes in both long and short-range order in material. X-ray powder diffraction studies carried out in a long time interval on copper based shape memory alloys reveal that peak locations and intensities chance with ageing duration in martensitic condition, and these changes lead to the martensite stabilization in the redistribution or disordering manner, and stabilization proceeds by a diffusion-controlled process.
06 Jan 1998
TL;DR: In this paper, a self-consistent relativistic spin-polarized version of the total energy full potential linearized augmented plane wave (FLAPW) method was developed on the basis of a second variation treatment of the spin-orbit coupling (SOC), and applied to determine the magnetoelastic coupling.
Abstract: 323 GQ-04. RELATIVISTIC SPIN-POLARIZED THEORY OF MAGNETOELASTIC COUPLING AND STRAIN DEPENDENCE OF MAGNETIC ANISOTROPY.* A. B. Shick. D. L. Novikov, and A. J. Freeman (Dept. of Phys. and Astronomy. Northwestern Univ., Evanston. IL 60208-3 I 12) A self-consistent relativistic spin-polarized version of the total energy full potential linearized augmented plane wave (FLAPW) method' is developed on the basis of a second variation treatment of the spin-orbit coupling (SOC), and applied to determine the magnetoelastic coupling. orbital magnetic moment anisotropy. and magnetic anisotropy energy (MAE) of a CO overlayer on Cu(001). The total energy as a function of perpendicular overlayerhbstrate strain is well titted by parabola and the MAE (-0.36 meV) at the equilibrium is in good agreement with experiment. As discovered earlier by Wu and Freeman.' we find a linear dependence of the MAE on the overlayerkubstrate distance. The calculated positive effective magnetoelastic coupling coefficient (1.13 meV) is caused by positive surface magnetoelastic anisotropy (0.23 meV). A relativistic total energy based model for ultrathin film magnetostriction yields a magnetostriction coefficient A,, = 5.20X IO-' and isotropic magnetostriction coefficient A,= -5.65X IO-' that is in very good agreement with previous studies based on a perturbative SOC treatment. The negative sign of the magnetostriction coefficient is caused by a positive surface magnetoelastic anisotropy. The substantial difference of magnetoelastic coupling coefficients for thin films. as opposed to bulk. is demonstrated. *Work at N.U. supported by the ONR (Grant No. N00014-94-1-0030). 'E. Wimmer, H. Krakauer, M. Weinert and A. J. Freeman, Phys. Rev. B 24, 864 (1981). 'R. Q. Wu and A. J. Freeman. J. Appl. Phys. 79. 6209 (1996). GQ-05. EFFECTS O F HETEROEPITAXIAL STRAIN ON THE LAVES PHASES DyFez AND TbFe2. Michael Huth, Brian Wiemeyer, and C. P. Flynn (Dept. of Phys.. Univ. of Illinois at Urbana-Champaign. I 110 West Green St., Urbana. IL 61801) The Laves-phase compounds DyFez and TbFe, are known for large magnetostrictions that exceed 0. I % at room temperature if the magnetic field is applied along the ( 1 1 I )directions. Such large magneto-elastic couplings should make it possible to tailor magnetic properties like the easy axis of magnetization. and to explore epitaxial clamping and strain for compounds grown heteroepitaxially on selected substrate templates. To this purpose DyFez and TbFez thin films grown by molecular beam epitaxy on various buffer layers were investigated. The preferred nucleation of the Laves phases in specific orientations was studied in situ on Ta ( 1 IO) and Ta ( I 1 1 ) buffer layers using RHEED, followed by further characterization using x-ray diffraction and atomic force microscopy. For thin buffer layers the residual elastic strain was used to vary the effective misfit between the buffer layer and the Laves phase whose thickness was kept at a fixed value. The resulting thickness dependence of residual strain in the Laves phase and its influence on the magnetic properties was studied by SQUID magnetometry in the temperature range of 4.2 K to 300 K. This work was supported by DEFG02-96ER45439 and ONR N0001L-941-0068. M. Huth thanks the Deursche ~ ~ r ~ c h u ~ g ~ g e m e i f l ~ c h ~ ~ for additional support. GQ-06. MAGNETO-MECHANICAL INSTABILITY IN FeTb/ Fe,FeCo MULTILAYERS. Manfred Wuttig*, Quanmin Su*. Eckhard Quandt**, and Alfred Ludwig** (*Dept. of Mater. Sci. and Eng., Univ. of Maryland, College Park, MD 20742-21 15, **Institut fuer Materialforschung I, Forschungszentrum Karlsruhe, Postfach 3640, 76021 Karlsruhe, Germany) Multilayers composed of alternate layers of Iron-RareEarth and Fe or FeCo alloys feature a high magnetostriction at low external fields and a coercive force as low as 5mT.'.*.' The coercive fields of as sputtered multilayers are significantly higher than that and the low values are attained after an anneal at 473K. Since the hysteresis remaining after the heat treatment might be of magneto-mechanical origin it is of interest to investigate the dynamic magneto-mechanical characteristics of this class of multilayers. Experiments on multilayers of the compositions (7nm FeTb)/(lOnm FeCo) and (7nm FeTb)/(8nm Fe) show a pronounced magneto-mechanical damping maximum and an attendant decrease of Young's modulus upon annealing. Both occur in the vicinity of the coercive field. Their evolution as a function of the annealing and magnetic field will be described and it will be shown that they reflect an instability4 principally caused by the magneto-mechanical interaction of the component layers of the multilayer. 'Jochen Betz, Ph.D. Thesis, Grenoble (1997). *Eckhard Quandt and Alfred Ludwig, Proc. MRS, vol. 459, p. 565-570 ( 1997). 'Jochen Betz. Kenneth Mackay and Dominique Givord, Proc. MRS, vol. 459 (1997). 'Manfred Wuttig, Quanmin Su, Y. Zheng, and Yiting Wen, Appl. Phys. Letters 67, 3641 (1995). GQ-07. MAGNETIC PROPERTIES AND MICROSTRUCTURE O F GIANT MAGNETOSTRICTIVE TbFelFeCo MULTILAYERS. E. Quandt, A. Ludwig (Forschungszentrum Karlsruhe GmbH, Inst. of Mat'ls. Res. I, P.O. Box 3640. D-78021 Karlsruhe, Germany), D. G. Lord, and C. A. Faunce (Univ. of Salford, Dept. of Phys., Salford M5 4WT,
TL;DR: In this paper, the critical magnetic field and electronic specific heat for dilute superconducting alloys of simple metals with transition metal impurities were calculated and applied to Al-iron group alloys.
TL;DR: In this article, a rapid-solidified Co-32 at%Ni foil and a stress-induced martensite phase was analyzed in temperature range of 77 to 673 K from observation of the texture, structure, magnetic property and Barkhausen noise.
Abstract: Ferromagnetic Co-Ni alloys of less than 35 at%Ni exhibit a phase transformation from γ-phase (FCC) to e phase (HCP): both phases are stable at higher and lower temperatures, respectively. Since both phases of these alloys exhibit high magnetization and thermoelastic martensitic transformation, it is expected as new ferromagnetic shape memory alloy. In this study, We prepared a rapid-solidified Co-32 at%Ni foil and analyzed thermoelastic and stress-induced martensite phase in temperature range of 77 to 673 K from observation of the texture, structure, magnetic property and Barkhausen noise. From these results, it is found that 1) the thermoelastic martensitic transformation is not reversible and 2) a stress-induced martensite phase is transformed to a austenite phase by heating. The result is caused by the mechanism of the transformation from a γ phase (HCP) to a e-phase (FCC).
TL;DR: In this article, alloys of composition Fe 3− x V x Si with x = 0.25, 0.50 and 0.75 were studied by neutron diffraction to obtain site distributions and information on magnetic ordering.