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  • 1
    Electronic Resource
    Electronic Resource
    Reply to the "Comment on: ‘The pinning force between a Bloch wall and a planar pinning site in MnAlC' '' (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1759-1759 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The boundary condition requiring continuity of (A/K)1/2 (∂θ/∂z) is discussed, where A and K are the exchange and anisotropy, respectively, θ is the spin orientation at the position z. This boundary condition is the result of the minimization of domain wall energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347224
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  • 2
    Electronic Resource
    Electronic Resource
    Structure and magnetic properties of rare-earth iron nitrides, carbides and carbonitrides (invited) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6017-6022 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Iron-rich rare-earth (R) compounds, such as R2Fe17 do not show great potential for high-performance magnet materials due primarily to their low Curie temperatures (Tc∼300–400 K). However, relatively large quantities of nitrogen or carbon atoms can be introduced into the structure, resulting in a dramatic enhancement of magnetic properties including Tc (≥700 K). The N or C atoms cause a volume expansion of a few percent of the unit cell without changing the crystal structure. The large increase in Tc can be attributed to the volume dependence of the Fe–Fe exchange interactions. A large uniaxial anisotropy field develops for R=Sm upon nitriding/carbiding with an anisotropy field that is almost double the value for Nd2Fe14B at room temperature. Problems including the precipitation of soft magnetic phases (mainly α–Fe) and the limited thermal stability of the nitrides have so far restricted the applications of these compounds. Here data are presented on combined carbide/nitride alloys prepared using a novel technique. These alloys exhibit many of the advantages of the pure compounds but with greater thermal stability and less interference from precipitated phases. A typical material, Sm2Fe17(NxC1−x)3−δ has a Tc of 758 K and an anisotropy field (μ0HA) of 15 T at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353456
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature dependence of coercivity in MnBi : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6275-6277 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In contrast to most ferromagnetic materials, the low-temperature phase of MnBi exhibits an increased coercivity, Hc, with temperature. μ0Hc has a value of 0.2 T at room temperature, and rises dramatically to a maximum value of 1.9 T at 550 K. In the temperature region near its maximum value, Hc is much larger than that of Nd-Fe-B and has a very-low-temperature coefficient. For this reason, MnBi has a great potential as a permanent magnet material at high temperatures. To describe the temperature dependence of Hc, we develop a hybrid domain-wall pinning model which combines Hilzinger and Kronmüller's scaling theory for an anisotropic domain wall with Gaunt's theory of thermal activation. The hybrid model gives an excellent fit to the temperature dependence of Hc and provides good estimates for the domain-wall energy and thickness over the temperature range studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352668
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of the chemical nature of transition-metal substrates on chemical-vapor deposition of diamond (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 4168-4173 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Chemical-vapor deposition of diamond on transition-metal substrates of Cu, Ni, Fe, and their alloys NiAl, Ni3Al, FeSi2, and FeSi has been investigated. It is shown that diamond grows easily on Cu with a very small amount of graphite, while on Ni and Fe there is rapid growth of the graphite layer before diamond deposition. The formation of graphite is attributed to the decomposition of carbon-containing precursors due to the strong catalytic reactivity of Ni and Fe substrates with carbon. The deactivation of these substrates by forming NiAl and FeSi2 results in the suppression of graphite and formation of high-quality diamond. However, for Ni3Al and FeSi substrates which are not completely deactivated, deposition of graphite still takes place. A mechanism based on the electronic structure of substrate atoms, particularly on the 3d shell structure of Cu, Ni, and Fe is proposed to understand the above behavior. Requirements for the stabilization of sp3 bonding of carbon on different substrates are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354420
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  • 5
    Electronic Resource
    Electronic Resource
    Specific heat measurements of pressure-induced reentrant superconductivity in Eu0.9Ho0.1Mo6S8 (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 1886-1891 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Specific heat measurements of Eu0.9Ho0.1Mo6S8 were performed using an ac calorimetry technique under the extreme conditions of low temperature, high magnetic field, and hydrostatic pressure. The title compound is a Chevrel phase material, which is paramagnetic at ambient pressure, becomes superconducting for pressures above 7 kbar, and has a reentrant upper critical field [dHc2(T)/dT≥0, as T→0 K]. Evidence that this material also has a high magnetic field-induced superconducting phase at low temperatures (H≥5 T, T≤1 K) was previously reported. The present ac calorimetry study carried out for 0.15≤T≤6 K, 0≤H≤20 T, and P(approximately-equal-to)8 kbar, shows a sharp superconducting transition for T≤1 K in the specific heat, which broadens at higher fields and temperatures. The results are analyzed to obtain a reentrant phase diagram in agreement with previous transport work, but direct evidence for the high field-induced phase was not found. The mechanism for the field and temperature dependence of the superconductivity of Eu0.9Ho0.1Mo6S8 is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353176
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  • 6
    Electronic Resource
    Electronic Resource
    Mössbauer study of intercalation modified compounds R2Fe17 (R=Y, Sm) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6038-6040 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mössbauer studies were carried out at 77 K in two series of R2Fe17 compounds with a magnetic (Sm) and nonmagnetic (Y) rare-earth, intercalated with H, C, and N. The increase in hyperfine field is largest at the 12j(18f) sites for R2Fe17H3.7 and R2Fe17N2.3. While the lattice expansion in R2Fe17C2 is similar to that in the nitrides and hydrides, the small change in hyperfine fields at the 12j(18f) and 12k(18h) sites indicates that the presence of neighboring carbon largely cancels the moment increase associated with the volume increase. For R2Fe17 carbonitrides, a single, sharp magnetic transition indicates a uniform compound. However, Mössbauer spectra suggest the existence of both C-rich and N-rich precipitates in the carbonitrides whose average hyperfine fields and isomer shifts scale with the nitrogen to carbon ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353462
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of Pb (ZrxTi1−x)O3 thin films produced by an automated laser ablation deposition technique (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5197-5207 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferroelectric lead zirconium titanate [Pb (ZrxTi1−x)O3] (PZT) thin films have been synthesized by using an automated laser ablation deposition technique with a capability for layer-by-layer or simultaneous deposition of elemental film constituents. The technique is suitable for producing multicomponent and/or multilayered thin films with controlled stoichiometry, such as high-temperature superconductor, ferroelectric, and electro-optic thin films. PZT films were synthesized on MgO (100) by either sequential deposition of layers of ZrO2, TiO2, and PbO, produced by laser ablation of ZrO2, TiO2, and PbO targets, or by simultaneous deposition of all species from ablation of stoichiometric or PbO-rich PZT targets. Films were deposited at 200 °C and subsequently annealed at 600 °C for different periods of time. The orientation, microstructure, surface topography, and composition of the films were characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Rutherford backscattering spectrometry, respectively. As-deposited layer films consists of highly oriented (001) PbO layers, from which highly oriented (110) PZT films are produced after postdeposition annealing. On the other hand, laser ablation of bulk PZT targets yields amorphous as-deposited films, which evolve into highly oriented (100) PZT films after postdeposition annealing. Preliminary electrical characterization of the PZT films included polarization hysteresis, fatigue, conductivity (ac and dc), and capacitance versus voltage measurements. From the initial electrical measurements, it appears that the remnant polarization of the layered PZT films is similar to that of the films produced by laser ablation of bulk PZT targets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353746
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  • 8
    Electronic Resource
    Electronic Resource
    Laser patterning of diamond films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3795-3801 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report here selective deposition and fine-scale patterning of hot filament deposited diamond films by the use of pulsed laser irradiation on silicon and copper substrates. The substrates were abraded with diamond and alumina powders before hot-filament chemical vapor deposition. A drastic enhancement in diamond nucleation (using hot-filament chemical vapor deposition) was observed on specimens treated with diamond powder, whereas enhancement on specimens pretreated with alumina powder was relatively insignificant. We have found that the seeding of diamond crystals was substantially reduced by pulsed laser annealing/melting which removes the plastic damage as well as the seed crystals introduced by diamond powder pretreatment. The selective deposition or fine-scale patterning of diamond films was achieved either by a shadow masking or by scanning a focused laser beam to generate desired patterns. The nucleation can also be enhanced by laser deposition of thin films, such as diamond-like carbon and tungsten carbide (WC), and selective deposition and patterning achieved by controlled removal or deposition of the above films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350892
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  • 9
    Electronic Resource
    Electronic Resource
    Isotope effects in amorphous silicon thin films produced by Ar-SiH4 -D2 plasma chemical vapor deposition method (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1678-1686 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ar-SiH4 -D2 gas mixture positive column plasmas and the deposition of (a-Si:D/H) thin films are investigated. Deuterated amorphous silicon thin films (a-Si:D/H) are produced in an Ar(95%)-SiH4(2.5%) -D2(2.5%) mixed gas plasma by employing dc positive column plasma chemical vapor deposition techniques. A twin probe electric field measurement is used to determine the plasma parameters. The reaction chamber wall temperature is measured by an infrared (IR) image camera. The results indicate that the uniformity of plasma is excellent; the wall temperature of the reaction chamber is nonuniform; and the deposition rate increases with increasing discharge power and gas pressure. The optical characteristics of isotopically different a-Si:H/a-Si:D films are also studied. The results show that the optical band gap of a film has a nonmonotonic thickness dependence with a significant isotope effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347212
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  • 10
    Electronic Resource
    Electronic Resource
    Domain wall pinning by magnetic inhomogeneities in Sm(CoNi)2.5 (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4592-4594 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Domain wall (thin 180° wall) pinning by pinning sites of atomic size is studied by a new model which is based on the argument that the temperature dependence of the coercivity originates from both thermal activation of the domain wall and the temperature dependence of the height of the energy barriers. This model successfully describes the temperature dependence of the coercivity of a Sm(CoNi)2.5 ferromagnet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344849
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