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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 899-905 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements of the dielectric behavior in the far infrared (10–200 cm−1) and in the microwave (8.5–12.5 GHz) regime for the conducting polypyrrole (PP) doped with tosylate anion. The dielectric constants have been determined from reflection and transmission data using the Fresnel equations. The magnitude and dispersive nature of the complex index of refraction is described for a number of samples with different levels of conductivity. The ability to tailor the dielectric behavior of these materials has been demonstrated by suitably reducing the oxidized PP films. The high reflectivity in the far infrared and microwave region cannot be accounted for in terms of the Drude model defining metallic behavior. An application exploiting the large real part of the index of refraction and relatively low loss observed in the microwave region is discussed.
    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 89 (2001), S. 7059-7061 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of [Co(tCo)/Pt(10 Å)]30 multilayers has been studied by x-ray absorption spectroscopy and x-ray diffraction using in-plane and out- of-plane polarized synchrotron radiation. The x-ray absorption near-edge spectroscopy shows that the Co layer is like a fcc pseudomorphic structure for tCo less than 4 Å. For tCo=10 Å, the spectra in both directions are separated and look closer to the bulk hcp Co. The extended x-ray absorption fine structure studies reveal that the Co–Pt interface of the multilayers fitted with a sharp boundary better than an interdiffusion model. The in-plane x-ray diffraction shows that the Pt layer in the multilayer possesses a 2%–3.5% compressible strain. Although the saturation magnetization Ms does not depend on tCo or interfacial roughness in any simple form, the Ms values scale quite linearly with the in-plane Pt strain. We conclude that the interfacial strain is important for the perpendicular magnetization in the Co/Pt multilayers. © 2001 American Institute of Physics.
    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 89 (2001), S. 7380-7382 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Mo(001) stepped surface was self-assembled on Al2O3(1-102) substrate by molecular beam epitaxy. Ni80Fe20 films were subsequently deposited on the fresh Mo(001) stepped surface at growth temperature (Tg) between 30 and 400 °C. Interestingly, in the low Tg regime (〈100 °C) the Ni80Fe20 films were grown as (001) single crystal while high Tg (〉300 °C) results in the growth of Ni80Fe20 (110) quadcrystal. For low Tg samples, the easy axis of the Ni80Fe20 film is directed parallel to the underlying Mo step edge direction and the M-H loop along the hard axis reveals a two-step magnetic moment rotation process. In contrast, the high Tg samples display isotropic-like magnetic behavior with a much enhanced coercivity due likely to the surface roughness effect. We conclude that the growth temperature of Ni80Fe20 film on the Mo stepped surface plays an important role on the crystal structure and magnetic anisotropy of Ni80Fe20 film. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co(11¯00)/Cr(211) and Co(112¯0)/Cr(100) multilayers have been simultaneously prepared on MgO(110) and MgO(100) substrates, respectively, by molecular beam epitaxy. They show however distinct magnetic anisotropic behavior which coincides with their magneto–crystalline anisotropy. Magneto–optical Kerr effect shows the existence of a unique easy axis and strong in-plane uniaxial magnetic anisotropy in Co(11¯00)/Cr(211) multilayers, which is induced by the well-defined hexagonal crystalline of the Co(11¯00) layers. For Co(112¯0)/Cr(100) multilayers, on the other hand, an in-plane biaxial magnetic anisotropy is found due to the bicrystalline structure of the Co(112¯0) layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial Co/Cr bilayered films have been successfully grown on the MgO(100) and MgO(110) substrates by molecular-beam epitaxy. According to the reflection high-energy electron-diffraction and x-ray-diffraction measurements the crystal structure of the film depends on orientation of the buffer and substrate. Epitaxial growth of biaxial Co(112¯0)/Cr(100) on MgO(100) substrate and of uniaxial Co(11¯00)/Cr(211) on MgO(110) substrate has been confirmed. The anisotropy magnetoresistance (AMR) is strongly influenced by the orientation of the Cr buffer. In Co(112¯0)/Cr(100) on MgO(100) AMR is isotropic for all in-plane fields. However, for Co(11¯00)/Cr(211) on MgO(110) we observed enhancement of AMR along the easy axis for temperatures below 150 K, while along the hard axis AMR has a local maximum at about 150 K. The easy axis data suggest that the longitudinal spin density wave of Cr and the crystal anisotropy of Co on Cr(211) plane dominate the enhancement of the AMR. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6276-6278 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co/Cu(111) multilayers, [Co(17 A(ring))/Cu(8 A(ring)〈tCu〈14 A(ring))]30, have been prepared on Co(70 A(ring)) buffer layers on Al2O3(0001) substrates by molecular beam epitaxy. From the longitudinal and transverse magnetoresistance (MR) measurements, it is observed that MRs consist of two components with a small anisotropic MR (〈2%) component at low field sitting on top of the giant MR (up to 22%) component at higher field. The AMR effect strongly correlates with the abundance of hcp stacking of Co, which tends to decrease with the increasing of Cu spacer thickness. The AMR saturation fields (1–3 kOe) coincides with those of the magnetization. It is suggested that the observed AMR effect is due to scattering from the hcp-phase Co layers in the multilayers. This together with the large saturation field (30–40 kOe) obtained from the entire MR curves indicate that the observed GMR effect may result from the Co-Cu interfacial spin-dependent scattering. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial Co/Cr multilayers, and single-crystal Co thin films etc. have been grown on MgO and Al2O3 substrates with Cr and Mo as buffer layers by molecular beam epitaxy technique. From the structure and magnetoresistance studies, we have found that the ferromagnetic anisotropy of resistance (AMR) is strongly influenced by the buffer layer, but with negligible effect due to the variation of the structure of Co films. The AMR of Co film on Cr buffer layer is quite small (0.1%); however, the MR of Co/Cr multilayers is almost one order larger than the AMR of Co film on Cr buffer layer. An enhancement factor of 4 for the MR in Co/Cr multilayers by the interface roughness has been observed. This suggests that the effect due to the spin dependent scattering at the interfacial regions of the superlattice is larger than that due to the spin dependent scattering in the ferromagnetic layers for the MR in the Co/Cr multilayer system.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Co/Cr superlattices with Co layer thickness of 15 A(ring) and Cr layer thickness of 10 A(ring) have been successfully grown on different substrates, such as MgO, Si, and quartz, by molecular-beam-epitaxy. The crystal structure of all samples has been characterized by in situ reflection high-energy electron diffraction. Both magnetoresistance (MR) and magneto-optical Kerr effect (MOKE) measurements were used to analyze the magnetic properties of these samples. Excellent epitaxial growth of hcp-Co(11¯00)/bcc-Cr(211) superlattices grown on MgO(110) was observed. Co/Cr superlattices were polycrystalline when grown on Si and amorphous when grown on quartz. Isotropic MRs of less than 1% were observed for all polycrystalline and amorphous Co/Cr superlattices. For Co(11¯00)/Cr(211) superlattices grown on MgO(110), a transverse MR of 14.2% and longitudinal MR of 0.67% were observed. MOKE hysteresis loops show perpendicular magnetization for polycrystalline Co/Cr superlattices grown on Si, and in-plane isotropic magnetization for amorphous Co/Cr superlattices grown on quartz. MOKE hysteresis loops for Co/Cr superlattices grown on MgO(110) show strong anisotropic behavior between the hard and easy directions. The magnetic properties of Co/Cr superlattices are strongly influenced by the crystal structure of Co and Cr which is controlled by the substrate. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2155-2157 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fcc-Co(110) and hcp-Co(11¯00) films of 200 A(ring) thickness were grown on MgO(110) and bcc-Cr(211)/MgO(110), respectively, by the molecular beam epitaxy method. Reflection high energy diffraction was used to in situ characterize the crystal structure. Co films grown directly on MgO(110) were pseudomorphic fcc structure. Twofold symmetrical hcp-Co(11¯00) films on top of the bcc-Cr(211)/MgO(110) were grown and confirmed. The magneto-optical Kerr effect (MOKE) was used to investigate the magnetic anisotropy of these films. The magnetization of these samples was found to be in-plane. The magnetization of fcc-Co films has cubic symmetry with texture induced uniaxial anisotropy. For hcp-Co(11¯00)/bcc-Cr(211) bilayer films, the magnetization was strongly anisotropic, but independent of the thickness of the Cr layer. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 7046-7048 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An hcp metastable phase of Ni80Fe20(11¯00) structure has been grown as high-quality epitaxial films on Co(11¯00) and Cr(211) planes. The epilayers of Ni80Fe20 grow as hcp structure up to a critical thickness of ∼100 Å, and the further layers transform to twinned fcc structure. Magneto-optical Kerr effect study indicates that the hcp Ni80Fe20(11¯00) layers exhibit strong crystalline induced uniaxial magnetic anisotropy with easy axis along the hcp[0001] direction. The subsequent fcc Ni80Fe20 layers show decreasing coercive fields as the film thickness increased. For the thick fcc film, interestingly, the magnetic easy axis shifts 90° with respect to that of the underlying hcp layers. The result is explained by the shape anisotropy effect due to the formation of quasi-1D columnar islands directed perpendicular to the hcp[0001] direction. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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