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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5845-5848 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mn- and Co-doped acicular γ-Fe2O3 particles with a coercivity of 923 Oe and Co content of 3.5 wt % have been prepared by a special process. This involves high-temperature ion diffusion, then step annealing. These particles exhibit a high magnetic thermal stability and low-temperature coefficient of coercivity. The latter demonstrates a striking contrast to the ordinary cobalt-body-doped γ-Fe2O3 particles. The induced uniaxial anisotropy constant Ku and the magnetocrystalline anisotropy constant K1 of the particles were determined by torque measurements. The novel properties of these particles are mainly due to the high uniaxial anisotropy, resulting from the anisotropic arrangements of cobalt ions. With the above characteristics and low Co content, these acicular particles can be one of the promising candidates for particulate high-density magnetic recording materials.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5335-5340 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The highly (110) textured Pb0.95La0.05(Zr0.7Ti0.3)0.9875O3 (PLZT) films have been successfully grown on SrTiO3(STO)-buffered silicon substrates. The films, deposited by pulsed laser deposition process, are assumed to form via a two-step process, i.e., cluster adherence and phase transformation. The beneficial effect of using STO as buffer layers involves enhancing the kinetics of phase transformation from amorphous phase to perovskite. The loss of Pb species from the films is thereby suppressed. The optimum dielectric constants obtained are around εr=490 for PLZT/STO/Si films deposited at 550 °C (1 mbar oxygen pressure, PO2) and post-annealed at 550 °C (1 atm PO2). The corresponding charge storage density is around Qc(approximately-equal-to)1.5 μC/cm2 at 50 kV/cm applied field strength. © 1995 American Institute of Physics.
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fine equiaxed γ-CoxFe2−xO3 (x=0, 0.06) particles with a diameter ranging from 200 to 1000 A(ring) were prepared by chemical precipitation. The average crystallite sizes were determined from x-ray line broadening measurements. The saturation magnetization and magnetocrystalline anisotropy of the particles were determined by using the approach to saturation. An empirical linear dependence of the specific saturation magnetization σs on the specific surface area Sa of the fine crystallites was obtained in the form of σs(S)=σs(∞)(1−ASa). The slope A which reflects the surface spin canting anomaly is different for γ-Fe2O3 and γ-Co0.06Fe1.94O3 particles. Under the supposition of the fine crystallite consisting of two parts, i.e., the surface layer, whose magnetic moment cannot be turned entirely along the direction of the applied field, but makes an average canting angle with the field, and the inner part, whose magnetic moment can be aligned along the direction of the applied field, the above formula can be interpreted well. The different slope A for γ-Fe2O3 and γ-Co0.06Fe1.94O3 particles may be caused by the different anisotropies of the two series particles.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7621-7626 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interdiffusion between layers in multilayer ferroelectric thin films was studied from their elemental depth profiles using secondary ion mass spectrometry. Among the films deposited on YBa2Cu3O7−x/CeO2/Si substrates, the interdiffusion is most pronounced for [Sr0.5Ba0.5]Nb2O6 (SBN) films, less marked for Pb0.97La0.03(Zr1−xTix)0.9925O3 (PLZT, x=0.54 or 0.34) films, and is least significant for BaTiO3 films. Higher substrate temperature used for growing SBN films is believed to be the main cause of interdiffusion. The larger proportion of cationic vacancies existing in PLZT films is another possible source inducing interdiffusion. Using YBa2Cu3O7−x/SrTiO3 as substrates substantially reduces the interdiffusion between layers. This is ascribed to the better crystallinity of the YBa2Cu3O7−x layers deposited on SrTiO3 substrates. These results indicate that both the characteristics of ferroelectric films and the underlying YBa2Cu3O7−x layers substantially modify the interdiffusion behavior between the layers. © 1996 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3442-3449 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of thermal energy (kBT), which has been found to play some important roles in the magnetic properties of recently developed antiferromagnetically coupled media, is described. It was observed that the thermal energy helps to obtain an antiparallel configuration of moments at remanence. Therefore, a reduction in the remnant moment–thickness product (Mrδ) is observed, even for smaller values of J (interface coupling constant) than those used in simulations that do not consider thermal energy. The magnetic viscosity measurement helps to distinguish the magnetization decay behavior of the top and bottom layers. The magnetic moments of top and bottom layers show maximum decay at different fields and the decay rates approximately scale with their thickness. Viscosity results also point out that the magnetization reversal of the bottom layer should occur in the first quadrant, in order to obtain a low noise and thermally stable media. Micromagnetic simulation was performed by including thermal effects. In that case, Mrδ reduction could be obtained for smaller values of J than in the case where thermal energy is not included in the simulation. © 2001 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 6994-6996 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: On the basis of a micromagnetic model, magnetization reversal in two antiferromagnetically coupled ferromagnetic layers (10 nm t1/0.9 nmM/t2 nm films with t2=2, 3, 4, 5 nm, here t1 and t2 are the top and bottom layers, respectively, and M the spacer) with the same random anisotropy arrangement can be represented by a computer simulation. The calculation indicates that the appearance of a full antiferromagnetic coupling at remanence requires the antiferromagnetic coupling constant j=−3.5 erg/cm2 for the 10 nm t1/0.9 nmM/3 nm t2, films and it needs a large j value if t2 increases for the case of Ku2=Ku1=1×106 erg/cm3 and Ms1=Ms2=400 emu/cm3. Hc follows the equation Hc=−0.755j/Mst1 (j〈0). Why the calculated Hc values deviate from Hcmax=−j/Mst1 is discussed. © 2001 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4997-4999 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dependence of the time decay of magnetization on orientation ratio was investigated for longitudinal Co–alloy thin film media. The coercivity orientation ratio was controlled by the degree of mechanical texture. For oriented samples, it was found that the remanent magnetization along the circumferential direction decayed faster with time than that along the radial direction when the applied reverse magnetic field was near the remanent coercivity. However, the remanent magnetization along the circumferential direction decayed more slowly with time than that along the radial direction when the applied reverse magnetic field was less than roughly half the remanent coercivity. Anisotropic interactions and magnetic anisotropy distributions appear to be the cause for the different time decay of magnetization along the circumferential and radial directions for oriented media. © 1999 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 5929-5935 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This study investigates the effects of CrAl underlayer and intermediate layer on the magnetic properties, crystallographic texture, and thermal stability of CoCrPtTa thin film media. Enhancement of coercivity and thermal stability factor of CoCrPtTa/CrAlx thin film media were observed when the Al concentration in the CrAl underlayer was varied from 0 to 14 at. %. We also observed an improvement in the in-plane crystallographic texture and a reduction in the magnetic switching volume and intergrain interaction. Results from the interdiffusion study using Auger depth profiling analysis, and ΔM measurement showed that the decrease of switching volume and intergrain interaction may be attributed to Al diffusion and/or Al-enhanced Cr diffusion into the grain boundary of the magnetic layer. Compared to CoCrPtTa/Cr media, we found that high coercivity, good in-plane crystallographic texture, and magnetic isolation for CoCrPtTa/CrAl media could be achieved at lower substrate temperature. This study has also shown that a CrAl intermediate layer could be used to further enhance the magnetic, crystallographic texture, and thermal stability properties of the CoCrPtTa thin film media. © 2002 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1179-1187 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A reduced set of neoclassical fluid equations, consisting of the parallel ion flow velocity v(parallel), the generalized potential F, the ion pressure p, and the parallel ion heat flow q(parallel), is derived. The resultant equations are the extension of reduced fluid equations derived from Braginskii equations with the high collisionality to the equations relevant to a fusion plasma with low to intermediate collisionality. The linear ηi mode dynamics is reinvestigated by using the resultant model equations. The effects of the perpendicular compressibility in the ion pressure response, the parallel heat flow, and the neoclassical viscosity are analyzed both analytically and numerically. It is stressed that the closure condition of neoclassical viscosity changes the sign of energy dissipation and seriously affects the stability of ηi modes.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3207-3216 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The poloidal variation of the parallel viscous and heat viscous forces are determined for the first time using a rigorous Chapman–Enskog-like approach that has been developed recently. It is shown that the poloidal variation is, like the poloidal distribution of the trapped particles, concentrated on the outer edge (large major radius side) of the tokamak.
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