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  • 1
    Electronic Resource
    Electronic Resource
    Observations of magnetization reversal and magnetic clusters in copper ferrite films : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6822-6824 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The observation of a magnetization reversal and a superparamagnetic behavior are reported for films of copper ferrite sputtered in an oxygen atmosphere. X-ray diffraction studies indicate the presence of 14-nm nanoscale crystals of CuFe2O4 in the films. Data on the temperature dependence of the film magnetization M for zero-field-cooled (ZFC) and field-cooled (FC) show that ZFC and FC curves separate at a temperature Tf and that Tf decreases with increasing static field strength. For T〈Tf, M vs T data for low fields indicate the presence of a compensation point in virgin samples. For T(approximately-greater-than)Tf, a superparamagnetic character is evident form the high-field magnetization data. An average cluster size of 16 nm obtained from such data is in excellent agreement with the results of x-ray diffraction studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356819
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetization and ferromagnetic resonance studies on amorphous films of Fe2O3-Bi2O3-Li2O : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6828-6830 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This report is on magnetic properties of samples of 0.5 Fe2O3-(0.5−x)Bi2O3-xLi2O (x=0.1–0.4) prepared in oxygen atmospheres by rf sputtering techniques. The films develop a spontaneous moment M only when annealed in air at temperatures Ta≥675 K. The room-temperature M vs Ta data show a maximum in M for Ta=775–875 K even though x-ray diffraction data do not show the precipitation of any crystalline ferromagnetic or ferrimagnetic phases. The spontaneous moment could be attributed to the presence of ordered clusters in the amorphous film. The magnetization is found to be dependent on the concentration of nonmagnetic Li2O: M increases with increase in x. An in-plane anisotropy in the films is evident from ferromagnetic resonance studies (FMR) at x-band frequencies. The anisotropy field increases with increasing x. The room-temperature in-plane FMR linewidth decreases with increasing x.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356798
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic and magnetoresistance studies on radio frequency sputtered La–Pb–Mn–O films : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5185-5187 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results on structural and magnetic characterization of radio frequency sputtered thin films of La0.74Pb0.26MnOz on (100) Si are presented. Stoichiometric films with a thickness of 0.6 μm showing (110) textured growth were deposited in a mixed argon–oxygen atmosphere. The low temperature magnetization is 10% smaller than the expected value for a collinear ferromagnetic order in the oxide. Zero-field resistivity data show a metal-to-semiconductor transition centered at Tms=250 K. Data on magnetoresistance (MR)=[ρ(0)−ρ(H)]/ρ(0) versus temperature reveal the following important features: (i) a maximum value of 22% for H=2 T at the metal-to-insulator transition temperature, (ii) MR value of 15%–22% over the entire temperature range 4.2–300 K, and (iii) a substantial MR, ∼10% even at temperatures as high as 380 K, well above the Curie temperature. Data on the temperature dependence of ferromagnetic resonance linewidth at 9.4 GHz show a discontinuity at Tms. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361333
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  • 4
    Electronic Resource
    Electronic Resource
    Instability mechanism of collective spin wave oscillations in finite-size ferrite samples : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5610-5612 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A sample-size effect on spin wave auto-oscillations under parallel pumping is studied experimentally in tangentially magnetized rectangular samples of yttrium-iron garnet (YIG) films where one of the in-plane sizes is varied. A previously developed one-dimensional theoretical model of unstable collective oscillations in the system of parametrically excited spin waves is used to describe the mechanism of spin wave auto-oscillations observed in YIG films. Our results show that the one-dimensional model (that works well for YIG spheres) gives only qualitative description of the sample-size effect in YIG films and the incorporation of the second finite size (film thickness) in this model is needed to achieve quantitative agreement with experiment in the film geometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355657
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  • 5
    Electronic Resource
    Electronic Resource
    The second-order spin-wave instability threshold in single-crystal yttrium-iron-garnet films under perpendicular pumping (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5433-5438 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The second-order spin-wave instability threshold in yttrium-iron-garnet single-crystal thin films has been investigated under conditions of ferromagnetic resonance (FMR). The samples were (111) etched circular films of 500 μm diam and 5.1 μm thickness, grown on gadolinium gallium garnet substrates by liquid-phase epitaxy. The pulsed microwave power FMR absorption curves were measured by standard signal averaging techniques at 9.18 GHz and room temperature for three different perpendicular pumping configurations: (1) in-plane static field and out-of-plane microwave field, (2) mutually perpendicular in-plane static and microwave fields, and (3) out-of-plane static field and in-plane microwave field. The experimental results show that the upsweep and downsweep FMR curves for lower pulsed microwave powers at low duty cycle of 1% are identical, but there are foldover effects in the FMR profiles at higher powers. Theoretical expressions for the instability threshold for these three configurations were obtained by extending previous theories. The calculated thresholds are in good agreement with the experimental results for configurations (1) and (2). The results for configuration (3) indicate the presence of a true foldover effect, also consistent with instability theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340364
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  • 6
    Electronic Resource
    Electronic Resource
    A microscopic model of energy deposition in silicon slabs exposed to high-energy protons (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 414-418 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A parameter free, microscopic model has been formulated to study the energy deposition due to protons bombarding silicon samples. The model is based on a Monte Carlo technique and uses two sets of essential and fundamental quantities from nuclear physics and condensed matter physics, the energy spectra and angular distributions of light fragments and heavy recoil nuclei from proton induced reactions, and the stopping power of ions through condensed media. Our model calculations are found to agree very well with the pulse-height spectra measured by McNulty, Farrell, and Tucker [IEEE Trans. Nucl. Sci. NS-28, 4007 (1981)] and by Farrell and McNulty [IEEE Trans. Nucl. Sci. NS-29, 2012 (1982)] for thin slabs of silicon (8.7–200 μm) exposed to protons at various energies (86–158 MeV). We present a critical analysis of the contributions of various spallation products to the total spectra and discuss the physical implications of such results for semiconductor devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339813
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  • 7
    Electronic Resource
    Electronic Resource
    Preludes to spin-wave chaos: Spin-wave instability processes, butterfly curves, kinks, flips, cusps, and shifts (invited) (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5401-5401 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Manifestations of chaos1–3 above the threshold microwave field for spin-wave instability have brought this established topic in microwave magnetics back into vogue. This paper will review the nature of the instability onset and the factors which determine the variation of the threshold microwave field for instability (hcrit) with dc field, the so-called "butterfly curve.'' A key factor here is the wave-vector k dependence of the spin-wave linewidth ΔHk. This k dependence leads to abrupt shifts in the wave number k for the unstable modes from large values (105 cm−1) to small values (103 cm−1) and a characteristic "kink'' in the subsidiary absorption butterfly curve. Under certain circumstances, flips in the aximuthal spin-wave propagation angle are also predicted. Such flips show up experimentally in some of the expected circumstances, but not in others.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342382
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  • 8
    Electronic Resource
    Electronic Resource
    Observation of auto-oscillations and chaos in subsidiary absorption in yttrium iron garnet (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5480-5482 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Auto-oscillations of the dynamic magnetization and routes to chaos for the first-order transverse pump spin-wave instability have been studied in single-crystal yttrium-iron-garnet (YIG) films. The measurements reported here were made on a 20.8-μm-thick YIG film at 9.4 GHz with the static and microwave fields in the plane of the film. Auto-oscillations at 100–400 kHz were observed in the power absorbed by the film over a relatively narrow static field range of 1100–1460 Oe, compared to the first-order instability (FOI) range of 0–1630 Oe. The auto-oscillation frequency and threshold microwave field amplitude were both strongly field dependent. The threshold amplitudes were about a factor of 2 larger than the FOI threshold amplitudes. At even higher power levels and for an even narrower field range of 1300–1380 Oe, the auto-oscillations showed frequency changes indicative of chaotic behavior. Several different subharmonic bifurcation routes to chaos were observed for different fields within the chaotic region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342353
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  • 9
    Electronic Resource
    Electronic Resource
    Light-scattering observation of anomalous parametric spin-wave character in subsidiary absorption (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5477-5479 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The technique of Brillouin light scattering has been used for the characterization, in terms of wave number and direction of propagation, of parametric spin waves associated with subsidiary absorption in thin films of yttrium iron garnet. Measurements at 7.99, 8.47, and 9.90 GHz have revealed a spin-wave character consistent with theory, with two notable exceptions. First, the data show no evidence for a predicted flip in the azimuthal propagation angle. Second, the measured magnon wave numbers at high fields are inconsistent with the theoretical values. The wave number and polar angle results imply that the change to low-k spin waves is not a discontinuous transition as indicated by the model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342524
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  • 10
    Electronic Resource
    Electronic Resource
    Brillouin light scattering detection of ferromagnetic resonance in thin films (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3344-3346 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic resonance (FMR) in thin films of permalloy and yttrium iron garnet (YIG) has been studied by Brillouin light scattering (BLS) techniques. The measurements were made at 9.4 GHz on 22.4 to 75-nm-thick permalloy films and on 2.1- to 12.8-μm-thick YIG films. Intensity profiles for magnon scattered light versus in-plane applied field were obtained by analyzing the forward scattered light through the films with a high-contrast Fabry–Perot interferometer. The BLS profiles show a signal-to-noise ratio of 10-100 for the permalloy and 100-1000 for the YIG films, depending on the film thickness and the microwave power level. The FMR BLS response was quantified in terms of global response function, counts/s mW versus magnon occupation number Nu. The Nu parameter relates the scattering to the uniform mode FMR response (linewidth, field, frequency, etc.), input microwave power, and active sample volume. The response for permalloy was approximately10−8 counts/s mW magnon, which translates into a limiting sample volume of 10−12 cm3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340802
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