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  • 1
    Electronic Resource
    Electronic Resource
    Elastic and anelastic properties of chemical vapor deposited epitaxial 3C-SiC (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5611-5615 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chemical vapor deposited 3C-SiC films were micromachined into free standing cantilevers and their anelastic and elastic properties were determined by a vibrating reed technique. Despite a high density of defects, epitaxial 3C-SiC exhibits extremely high mechanical Q which is essential for resonator sensors and actuators. An anelastic relaxation peak was found with an associated activation energy of 0.94 eV. Doping caused splitting of this peak. The mechanism of the mechanical relaxation peak is discussed in relation to defect movement under stress. Young's modulus of epitaxial undoped 3C-SiC was found to be 694 GPa, p-doping reduced it to 474 Gpa. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359551
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal expansion of Ni/Cu multilayers (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4567-4570 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The coefficient of thermal expansion of electrodeposited Ni/Cu multilayers was obtained by measuring the evolution of membrane resonances and hence the tension as a function of temperature. The apparent thermal expansion coefficient of the multilayer membranes increases as the interface density of the multilayers increases. This increase is analyzed in terms of stress relaxation resulting from sliding of nonperfectly bonded interfaces. The analysis permits the normalization of all thermal expansion data of the Cu/Ni multilayers with layer thicknesses ranging from 20 to 800 nm but not of the thinnest layers, 2 nm thick. The results are consistent with the idea that interfacial adhesion improves as the layer thickness becomes very small, favoring epitaxial growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357289
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  • 3
    Electronic Resource
    Electronic Resource
    Stresses in chemical vapor deposited epitaxial 3C-SiC membranes (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1280-1283 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The internal stresses in chemical-vapor-deposited 3C-SiC films were studied by a vibrating membrane technique. The differential thermal expansivity of 3C-SiC films was investigated by the change of the internal stress as a function of temperature. It was found that the internal stress of the films is dominated by thermal stresses and its magnitude depends both on doping and the film thickness. While p doping substantially increases the stress, increasing the film thickness reduces the stress of the SiC layer. The thermal expansivity of the SiC layer shows a lower value which is significantly less than that of bulk 3C-SiC and tends to approach the expansivity of the Si substrate. It is proposed that the stress dependence of the SiC films on doping and film thickness is the result of the film morphology which is heavily faulted for very thin films and more perfect as the film thickness increases. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359579
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  • 4
    Electronic Resource
    Electronic Resource
    Micromachined silicon torsional resonator for magnetic anisotropy measurement (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 3908-3912 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel method for measuring the out-of-plane magnetic anisotropy of thin films has been developed using the existing techniques of silicon micromachining. The torsion pendulum, which is commonly used to measure the perpendicular magnetic anisotropy energy constant, Ku, is modified into a single crystal silicon high Q torsional resonator. This article describes the principle of a silicon torsional resonator, the experimental procedure for measuring magnetic anisotropy, and the results. The theoretical values of Ku for Terfenol-D and Metglas® thin films were compared to the experimentally determined values and found to be within the error limits which for Metglas©, better than 1%. The agreement is poorer, 5%–15%, for amorphous stressed Terfenol-D, since its magneto-elastic energy is less accurately known. The results show that this is a viable method for measuring the magnetic anisotropy. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149198
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  • 5
    Electronic Resource
    Electronic Resource
    Occurrence of ferromagnetic shape memory alloys (invited) (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4707-4711 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article presents an overview of the necessary conditions for the formation of shape memory alloys (SMAs) and how these must overlap with the occurrence of ferromagnetism so that ferromagnetic shape memory alloys (MSMAs) may be formed. The electronic, elastic, and geometric conditions permit an understanding of the occurrence of Cu- and Fe-based SMAs as well as NiMnGa Heusler MSMAs except that the naively determined critical electron concentration for the latter, 7.3, disagrees with the values of 1.5 and 8.6 accepted for the Hume–Rothery phases and certain Fe-based systems. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373135
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  • 6
    Electronic Resource
    Electronic Resource
    Magneto-mechanical instability in Terfenol-D films (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3641-3643 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tensioned 1 μm nanocrystalline Terfenol-D films on 50 μm Si substrates display a pronounced damping maximum at a magnetic field of about 1.5 kOe oriented perpendicular to the plane of the film. The phenomenon is critically dependent on the orientation of the magnetic field and is the result of a magnetomechanical instability in the Terfenol film. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115344
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  • 7
    Electronic Resource
    Electronic Resource
    Internal strain relaxation and the glassy behavior of La-modified lead zirconate titanate relaxors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6595-6602 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonlinear internal friction measurements have been carried out on La-modified lead zirconate titanate relaxors with a Zr/Ti ratio of 65/35. Measurements have been made as a function of La content and dc bias. The elastic softening is believed to have a ferroelastic contribution due to the tilting of the oxygen octahedra, in addition to the expected electrostrictive effects. The temperatures of the maximum softening form a plausible extension to the rhombohedral-rhombohedral phase boundary [Proc. IEEE 61, 959 (1973)]. A frequency dependence of the softening has also been found which was interpreted as the existence of fluctuations in the orientations of the tilts. These fluctuations are proposed to arise in an attempt to partially relieve an inhomogeneity in the electrostrictive strains associated with the polarization fluctuations. The results are discussed in context with previously reported transmission electron microscopy work [C. Randall, Ph. D. dissertation, University of Essex (1987)]. Dielectric measurements have also been done as a function of La content and bias, and the freezing temperature of the polarization fluctuations determined as a function of composition. A revised phase diagram has been proposed using this data base which shows different phase fields having various combinations of freezing mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348871
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  • 8
    Electronic Resource
    Electronic Resource
    Local polar configurations in lead magnesium niobate relaxors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 414-419 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The field dependence of the dielectric response has been measured for lead magnesium niobate relaxors. The frequency dispersion of the temperature of the permittivity maximum, Tmax, was analyzed using the Vogel–Fulcher relationship. The field dependence of the permittivity at various temperatures was also modeled using a phenomenological expansion in the electric field. The activation energy and a softening of the dielectric response were found to be maximum under a small bias. The freezing temperature was found to be minimum near this same bias. These results are interpreted to mean that the moments of the polar clusters do not freeze in random orientations, but rather locally preferred configurations of moments are proposed to exist. Evidence is presented that the scale of these configurations is approximately 100 A(ring). At higher biases the relaxation mechanism was shut down; consequently, the nonlinear response was stiffened and Tmax increased. The nonlinear response was also found to be maximum near the freezing temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347732
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  • 9
    Electronic Resource
    Electronic Resource
    Freezing of the polarization fluctuations in lead magnesium niobate relaxors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2916-2921 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dielectric relaxation of a solid solution of 10-mol % lead titanate in lead magnesium niobate is found to be similar to the magnetic relaxation in spin-glass systems.1–3 Based on this analogy, it is proposed that the relaxor ferroelectric is a polar-glassy system which has thermally activated polarization fluctuations above a static freezing temperature. An activation energy and freezing temperature of 0.0407 eV and 291.5 K, respectively, were found by analyzing the frequency dependence of the temperature of the dielectric maximum using the Vogel–Fulcher relationship.4,5 It has also been shown that a macroscopic polarization is sustained on heating up to this freezing temperature. A coupling between nanometer scale clusters is believed to control the kinetics of the fluctuations and the development of a frustration as the system freezes into states of local equilibrium. The possibility of an orientational freezing associated with the ferroelastic nature of the nanosized polar regions in the rhombohedral relaxor families as well as a polar freezing is discussed. A diffuse phase transformation is believed to arise due to a dispersion in the fluctuation frequency of the polarization. A qualitative model for the relaxation time spectrum is also proposed in which the width of the spectrum broadens strongly near the freezing temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346425
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetomechanical instability in FeTb/Fe multilayers : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7264-7266 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multilayers composed of alternate layers of iron–rare earth and Fe or FeCo alloys feature a high magnetostriction at low external fields and a coercive force as low as 5 mT. The coercive fields of as sputtered multilayers are significantly higher than that and the low values are attained after an anneal at 473 K. Since the hysteresis remaining after the heat treatment might be of magnetomechanical origin it is of interest to investigate the dynamic magnetomechanical characteristics of this class of multilayers. Experiments on multilayers of the composition (7 nm FeTb)/(8 nm/Fe) show a pronounced magnetomechanical 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 instability principally caused by the magnetomechanical interaction of the component layers of the multilayer. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367753
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