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  • 1
    Electronic Resource
    Electronic Resource
    Direct observation of magnetization dynamics in spinning magneto-optic discs (invited) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5776-5781 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The development of a system capable of direct observation of magnetization and thermal dynamic behavior of magneto-optic recording materials at various relative media-to-laser spot velocities is described along with demonstrations of its value in furthering the understanding of such behavior. A 10-ns-wide observation laser pulse is utilized to produce "stop-action'' images of magnetization states in an environment almost identical to that of an actual magneto-optical disc drive operating at linear velocities of 0–40 m/s (7200 rpm, 53 mm radius). Thermal modeling is correlated with images of the instantaneous temperature distributions at various velocities to demonstrate that the thermal conductivity in the materials is approximately 7 W/m/K rather than the bulk 40–50 W/m/K. Techniques for isolating signal due to moving magnetization reversal regions from that due to moving areas of elevated temperature are used to analyze the writing behavior of single layer direct-overwrite recording films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353570
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of random coercivity on domain growth processes in rare earth–transition metal alloys (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4856-4856 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the present investigation, we show that local fluctuations of the magnetic properties in amorphous alloys, specifically the fluctuating anisotropy, can cause irregularity in the domain shape which has been attributed to causing writing noise.1 We propose a model for coercivity based on the pinning of domain walls by the randomly fluctuating anisotropy constant. This model is believed to be particularly suitable for materials containing non-S-state rare-earth ions like terbium, because the 4f electrons of these ions, through the spin-orbit coupling, interact strongly with the random local electrostatic fields. A computer model developed to simulate dynamic domain wall motion2 is used with a new coercive force model to predict the domain growth process. The effects of the random coercivity on the shape of the written domain were studied for two different processes: (a) thermomagnetic writing by a laser beam and (b) wall motion by thermal activation at a constant temperature. It is shown that domain shape distortion becomes more pronounced as the percentage of the random anisotropy relative to that of the constant anisotropy is increased, particularly in the case of thermal activation.〈ks〉
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348227
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  • 3
    Electronic Resource
    Electronic Resource
    Separation of perpendicular anisotropy components in dc-magnetron sputtered TbFe amorphous films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7202-7206 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Different anisotropy components originating from various mechanisms in dc-magnetron sputtered Tb39Fe70 films have been identified. The inverse magnetostrictive anisotropy component was determined by comparing the anisotropy of Tb30Fe70 films when they were removed from their substrates and when they were still attached to their substrates. The single-ion anisotropy component was then derived by subtracting the pair-ordering anisotropy, which was determined as the anisotropy of Gd21Fe79 films which had been removed from their substrates, from the anisotropy of Tb30Fe70 films which had been removed from their substrates. By this method, single-ion and inverse magnetostrictive anisotropies were found to contribute 30–60% and 30–65%, depending on argon sputtering pressure, of the total anisotropy, respectively. Pair-ordering was responsible for less than 10% of the total anisotropy in dc-magnetron sputtered Tb30Fe70 films. Thermal stability of each anisotropy component was studied by annealing films when still attached to their substrates. The anisotropies of films, which had been annealed and removed from their substrates were then compared with those of films, which had also been removed from their substrates but without annealing. Effects of Ar sputtering pressure on the thermal stability of anisotropy were also investigated. Better thermal stability was found in single-ion and pair-ordering anisotropy than in magnetostrictive anisotropy. Films deposited at lower argon pressures show better thermal stability of single-ion and pair-ordering anisotropy than those deposited at higher argon sputtering pressures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347613
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  • 4
    Electronic Resource
    Electronic Resource
    Domain erasure and formation in direct overwrite magneto-optic recording (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5293-5299 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The erase and write processes in single layer direct-overwrite magneto-optic recording materials were investigated utilizing a stroboscopic microscope system with 10-nsec time resolution. The effects of thermal magnetization reduction are addressed and limited by image subtraction techniques. With this technique the erase process is shown to be a collapse process which occurs during heating, rather than cooling. Galvanometer driven beam scanning is utilized to write and erase "stripe'' domains at velocities up to 5 m/s. Scanning write and scanning continuous beam erase are investigated stroboscopically, providing surprising new data on these processes. The erase process for a "stripe'' domain is shown to proceed from the end of the domain, and in front of the approaching erase laser beam. Jitter in the leading edge of the written domain is observed, and may be responsible for the noise levels observed in these materials. The data indicate that the erase process is driven by a combination of temperature and temperature gradient. The write behavior can be explained by either a post-laser pulse nucleation or by movement of the trailing domain wall.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347021
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  • 5
    Electronic Resource
    Electronic Resource
    A mass-independent sulfur isotope effect in the nonthermal formation of S2F10 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 6099-6109 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A non-mass-dependent sulfur isotope effect is present in the rotationally symmetric S2F10 molecule, produced in an electrical discharge through sulfur tetrafluoride. A similar isotopic fractionation was observed in the product S2F10 from the electrodissociation of SF5Cl, and reaction between fluorine atoms produced by F2 photolysis and SF4, collectively ruling out the SF5 formation process as the source of the mass-independent fractionation. The mass-independent mechanism is shown to occur in the SF5+SF5→S2F10 formation step. The secondary dissociation of S2F10 as a source of the mass-independent fractionation is ruled out by control S2F10 dissociation experiments which are shown to produce small mass-dependent fractionations. Mass-dependent effects such as sulfur isotopic exchange and secondary dissociation reactions are significant processes for the system under study and have been quantitatively accounted for. The role of symmetry in non-mass-dependent isotope effects is strengthened by the present experiments, and the search and characterization of mass-independent effects is extended to sulfur-containing molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456375
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of substrate roughness on microstructure, uniaxial anisotropy, and coercivity of Co/Pt multilayer thin films : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6864-6866 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We studied the microstructure and magnetic properties of Co/Pt multilayer thin films sputtered onto glass and Si substrates with different surface roughness caused by different methods of substrate preparation. The microstructure determined by high-resolution electron microscopy and x-ray scattering could be correlated to the observed magnetic properties. Better (111) texture and smoother layer structures produced on smoother glass substrate surfaces produced higher uniaxial anisotropy. Coercivity, on the other hand, was enhanced by either pinning of the domain walls caused by substrate surface roughness or stronger columnar structure. Although Si substrates exhibited slightly different roughness under the same preparation conditions, the dependence of magnetic properties on the substrate surface was consistent with the trends using glass substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356810
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of Ba content on grain size and dynamics of crystallization in barium ferrite thin films : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4380-4382 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of Ba content on the dynamics of the crystallization process, which ultimately determines the grain size, were studied in barium ferrite thin films. Rapid thermal annealing was used to crystallize the amorphous as-deposited barium ferrite films. The annealing time and temperature dependent crystalline volumes were determined from the magnetization of the films, and were analyzed by means of the Johnson–Mehl–Avrami relation. Microstructural studies showed that the films with higher Ba content had higher nucleation rates and lower growth rates; consequently, they had finer grain size and smaller grain aspect ratio. Magnetic measurements showed that the higher Ba content films also had higher coercivities and smaller magnetic switching volumes. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364830
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  • 8
    Electronic Resource
    Electronic Resource
    Study of the angular-dependent exchange coupling between a ferromagnetic and an antiferromagnetic layer (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2687-2689 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The angular dependence of the exchange coupling between a Permalloy film and an antiferromagnetic Cr45.5Mn45.5Pt9 film has been measured. We show that this complex angular dependence of the exchange coupling can be understood by a simple Stoner–Wohlfarth model involving only a uniaxial anisotropy and a unidirectional exchange coupling at the interface. Numerical results are in excellent agreement with the experimental data. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123937
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  • 9
    Electronic Resource
    Electronic Resource
    Ba doping and rapid cooling effects on coercivity of Bi-Dy-Al-Fe garnet films for magneto-optical recording prepared by pyrolysis (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1125-1126 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Al-doped Bi-Dy iron garnet films have been fabricated by the pyrolysis method on glass substrates, and the effects of Ba doping and rapid cooling on the coercivity (Hc) were investigated. Films were quenched from 660 °C to room temperature within about 120 s. Rapid cooling causes a rise of Hc, and a small amount of Ba doping enhances this effect. Hc values near 4200 Oe at room temperature were obtained in rapidly cooled films with the composition Bi1Dy1.96Ba0.04Fe4.4Al0.6O12.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100662
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  • 10
    Electronic Resource
    Electronic Resource
    Barium ferrite thin film media with perpendicular c-axis orientation and small grain size (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 6370-6372 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Barium ferrite thin films with perpendicular c-axis orientation and small grain size (about 300 Å) were successfully fabricated with careful control of sputtering conditions. The c-axis orientation of barium ferrite thin films is most sensitive to the oxygen partial pressure during deposition. All samples with oxygen gas during deposition have a random c-axis texture, as indicated by existence of both weak (00l) peaks and (106) peaks. All the samples without oxygen gas during deposition show only strong (00l) peaks, which indicate excellent perpendicular c-axis orientation. Transmission electron microscopy results show that oxygen gas promotes the growth of in-plane and/or randomly oriented grains. The effect of the Pt interlayer on the barium-rich films was also studied. The Pt interlayer was found to be very effective in improving c-axis orientation of barium-rich films. A relative increase in perpendicular nucleation sites over in-plane and/or random nucleation sites contributes to the improvement in perpendicular c-axis orientation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372709
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