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  • 1
    Electronic Resource
    Electronic Resource
    Thermal magnons in bcc cobalt-itinerancy and exchange stiffness (invited) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6120-6125 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stable hcp and the metastable bcc phases of cobalt have almost identical nearest-neighbor distances, but substantially different coordination numbers z (zbcc=8, zhcp=12). While z is central to magnetic behavior in insulating systems, these distinctive structural features of cobalt offer an opportunity to address the role of coordination in strong itinerant ferromagnets. We report a room-temperature Brillouin scattering study of surface and bulk spin waves in molecular-beam-epitaxially grown thin films of bcc cobalt. Fitting expressions for the surface and bulk magnon dispersion to the measured frequency shifts versus applied magnetic field provides values for the gyromagnetic ratio, saturation magnetization M, and the exchange stiffness constant D for bcc cobalt. Our results reveal that M is about 10% lower than that of the hcp phase, while D scales with z, a characteristic of an insulating ferromagnet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348778
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  • 2
    Electronic Resource
    Electronic Resource
    Elastic constants of face-centered-cubic cobalt (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6005-6009 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The wave vector dependence of Rayleigh and higher order Sezawa elastic waves in single crystalline epitaxial face-centered-cubic (fcc) Co layers are measured by Brillouin light scattering at room temperature. The dispersion of the mode velocities allows the independent elastic constants to be determined for this cubic phase of cobalt. These results compare very favorably to previous determinations of the elastic constants measured above 700 K from the high-temperature fcc phase of pure Co. Deviations from theoretical estimates are discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371647
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  • 3
    Electronic Resource
    Electronic Resource
    Elastic properties of chemically ordered Co3Pt thin films (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2737-2741 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report room temperature Brillouin light scattering measurements designed to probe the elastic properties of chemically ordered Co3Pt alloy films. A series of 100 nm thick films were deposited by molecular beam epitaxy at different growth temperatures (Tg) between 450 and 950 K. As the deposition temperature increases the lattice structure is observed to transform from a compositionally disordered, mixed fcc/hexagonal phase to a compositionally ordered, purely hexagonal phase, and finally to a compositionally disordered fcc phase. These structural transitions are accompanied by large changes in magnetic anisotropy, new features in the magneto-optical Kerr effect, and changes in the magnetic domain widths which all occur within about a 100 K temperature window centered around Tg=650 K. However, the independent elastic constants show no significant changes in the different films. These findings suggest that macroscopic strain effects are unlikely to underlie the diverse magnetic signatures observed within the chemically ordered phase. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1433924
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetic anisotropies in thick body centered cubic Co : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5387-5389 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic anisotropies of a 357-A(ring)-thick Co film in the bcc phase were examined using Brillouin light scattering. This film, one of the thickest known bcc Co structures, is found to have a fourfold magnetic anisotropy that is markedly different from those of thinner films. A large possibly strain-induced uniaxial anisotropy is also found. The film is thick enough so that the surface and n=1 bulk magnon are within a few GHz of each other and strongly hybridize. Unusual behavior of the scattering intensities suggest the possible presence of surface anisotropies and/or inhomogeneous internal fields. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362312
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  • 5
    Electronic Resource
    Electronic Resource
    Optical transitions in (ZnCo)Se and (ZnFe)Se: Role of an effective p–d exchange (invited) : 38th Annual Confrerence on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5719-5724 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we discuss photoluminescence (PL) and Raman excitations in the diluted magnetic semiconductors Zn1−xCoxSe and Zn1−xFexSe. The PL spectra associated with isolated crystal field d levels are found to rapidly weaken and/or broaden as the transition metal ion concentration approaches and increases beyond a critical value. In addition a Raman continuum, that overlaps with the optical phonon, is observed to develop when the PL features are modified. In the corresponding Zn1−xCoxSe samples the optical phonons acquire a characteristic Fano line shape suggestive of its coupling to the Raman continuum. It is proposed that these changes to the optical transitions arise from the enhancement of an effective p–d hybridization between low-lying d levels and band electrons with increasing x—an effect largely due to the proximity of the Co2+ and Fe2+ crystal field ground levels to the valence band maximum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355594
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  • 6
    Electronic Resource
    Electronic Resource
    Observation of magnons by light scattering in epitaxial CoFe/Mn/CoFe trilayers : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3785-3787 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on Brillouin scattering measurements on a CoFe/Mn/CoFe trilayer film characterized by unusually large biquadratic coupling. The magnetic field dependence of the exchange coupled in- and out-of-phase magnons as well as their in-plane directional dependence are determined. The saturation magnetization of the trilayer was measured independently through superconducting quantum interference device magnetometry. The spin wave data is well represented by a generalization of the model that takes into account the antiferromagnetic order in the Mn layer. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364769
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  • 7
    Electronic Resource
    Electronic Resource
    Elastic properties of nanocrystalline zirconium–silicon–boron thin films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4349-4353 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin amorphous films of ZrB3 grown on Si(111) substrates by chemical-vapor deposition are, upon annealing at 960 °C, transformed to films composed of nanocrystallites (6–10 nm extent) with a nominal composition of Zr0.9Si0.3B3. The independent elastic constants of the layers are determined from the dispersion of the surface and pseudo-Sezawa acoustic excitations and reveal large enhancements in the C11 and C44 constants accompanying the conversion of ZrB3 to the nanocrystalline phase. Since the transverse sound velocities of the binary and Zr0.9Si0.3B3 are in near resonance with the sound velocity of Si (VTSi=4.8 km/s), only the Rayleigh surface wave is localized to the film while all higher-order acoustic modes are evanescent. Despite the strong decay channels, high-lying excitations with velocities as large as 25 km/s ((very-much-greater-than)VTSi) are observed in Brillouin light scattering. Insight into these acoustic properties is provided by evaluating the elastodynamic Green's functions and associated acoustic-mode densities. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1354632
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  • 8
    Electronic Resource
    Electronic Resource
    Dispersion of elastic waves in supported CaF2 films (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3407-3410 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The velocities of the principal and several higher-order elastic modes localized in CaF2 films grown epitaxially on Si(111) have been measured using Brillouin scattering. The effective elastic constants of the epilayers are evaluated from a fit to the mode dispersion. With decreasing film thicknesses from about 1500 A(ring) reductions from the bulk elastic constants are found. Thicker films are well characterized by bulk parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342657
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  • 9
    Electronic Resource
    Electronic Resource
    Correlation of superconducting properties and oxygen concentration in Y1Ba2Cu3O7−δ films via Raman spectroscopy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3598-3601 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report Raman scattering and resistance measurements on a YBa2Cu3O7−δ film in which δ is varied by repeated annealing in oxygen or argon. As oxygen is removed, the resistance rises, the transition moves to lower temperature and broadens, and "forbidden'' Raman modes are observed. Group theory, the Raman activity of another oxygen rich (δ∼0) film of different orientation, and comparison with results on single crystals allow us to assign each Raman phonon. We hence demonstrate that several "forbidden'' Raman peaks are associated with depletion of oxygen chain sites. Our results establish that the oxygen concentration δ, and hence the superconducting properties, can be varied reversibly by reannealing in oxygen or argon with the Raman spectra providing a useful microscopic probe of the lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341395
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  • 10
    Electronic Resource
    Electronic Resource
    Exchange stiffness and magnetic anisotropies in bcc Fe1−xCox alloys : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7021-7023 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Brillouin scattering measurements from several bcc Fe1−xCox epitaxial films are reported. The magnetic-field dependence of the spin-wave spectrum as well as the in-plane directional dependence of the surface magnon are determined. The saturation magnetization of the alloys was measured independently through superconducting quantum interference device magnetometry. Self-consistent fitting of the magnon dispersions determined from the separate Brillouin experiments provide values for the concentration dependence of the exchange stiffness D, the fourth-order crystalline cubic anisotropy K1, and surface anisotropies Ks and Ks,p. In agreement with ferromagnetic resonance data, K1 is found to change sign for x beyond about 35 at. % while D steadily increases with cobalt concentration up to x∼0.5 and subsequently decreases in two Co-rich samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356763
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