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  • 1990-1994  (3)
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  • 1
    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
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7021-7023 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6120-6125 
    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
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