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  • 1
    Electronic Resource
    Electronic Resource
    Ferromagnetic resonance in Ag coupled Ni films : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6341-6343 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present an X-band ferromagnetic resonance (FMR) study of polycrystalline single Ni films and of two Ni layers separated by an Ag layer at room temperature. Films were deposited by sputtering on glass using Ag over- and underlays. The single Ni films have a FMR mode with a dependence of the resonance field on the angle α between the magnetic field and the plane in good agreement with theory. In samples with two Ni films coupled through an intervenient Ag layer, only one FMR mode is observed if the two Ni have identical thicknesses. When the films have different thicknesses a second weak resonance appears. The field difference between the two modes is a measure of the coupling between the Ni films. Results were obtained for a series of samples with the Ag thickness varying in the range 10≤t≤30 A(ring). Surprisingly, the two modes have opposite behavior with the variation of α, for all values of t. The results suggest that the coupling is antiferromagnetic when the field is parallel to the film plane and ferromagnetic when perpendicular, regardless of t.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352642
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  • 2
    Electronic Resource
    Electronic Resource
    Spin-wave self-oscillations: Experimental verification of the two-mode origin (invited) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 6805-6810 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Most theoretical models used to explain self-oscillations and chaotic phenomena observed in microwave pumped spin-wave instabilities are based on the assumption that the dynamics is governed by a few interacting modes. This assumption is somewhat disturbing because it is known that in principle an extremely large number of modes can be excited when the microwave field h exceeds the Suhl instability threshold hc. In this paper we describe pulsed microwave (8.2 GHz) spin-wave pumping experiments in spheres and films of yttrium–iron–garnet which clearly demonstrate that, with increasing power, one mode is excited at h=hc, a second mode appears at h(approximately-greater-than)hc, and subsequently the self-oscillation sets in. The observations agree very well with computer results for the transient behavior of the spin-wave equations, showing that the two-mode assumption for the onset of self-oscillation is correct. We also present data for films which add evidence to the sample-size dependence of the self-oscillation frequency and support recent improvements proposed for the two-mode model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352492
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  • 3
    Electronic Resource
    Electronic Resource
    Controlling spin-wave chaos : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5613-5615 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Microwave pumped spin-wave instabilities in YIG spheres were one of the first experimental systems used to demonstrate that chaos can be suppressed by small periodic modulations in an accessible system parameter. Here we show that the equations describing two interacting spin-wave modes account satisfactorily for the experimental results, as long as the field modulation is appropriately introduced in the model. The finite detuning parameters expressing the boundary conditions of the sample provide a natural way for introducing the field modulation. Thus the present results constitute additional evidence of the validity of the two-mode model with momentum-nonconserving driving Hamiltonian used to explain the sample size dependence of the self-oscillations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355658
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  • 4
    Electronic Resource
    Electronic Resource
    Spin-wave chaotic transients : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5616-5618 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the observation of transient chaotic spin-wave auto-oscillations in X-band pulsed subsidiary-resonance experiments in a YIG sphere. Chaotic transients to a periodic attractor have been observed near a critical microwave power pc∼10 dB relative to the Suhl instability threshold. By an averaging of 100 randomly chosen initial conditions at each power, we estimate a critical exponent γ ∼ 0.57. In addition, we demonstrate that the results can be qualitatively understood within the framework of the standard two-mode model. Numerical simulations yield, for a particular set of parameters, chaotic transients obeying the predicted scaling law with a critical exponent γ ∼ 0.54.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355659
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  • 5
    Electronic Resource
    Electronic Resource
    Biquadratic exchange coupling in sputtered Fe/Cr/Fe(100) sandwich structures : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 3791-3793 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used magnetoresistance, magneto-optical Kerr effect, ferromagnetic resonance (FMR), and Brillouin light scattering to investigate interlayer exchange coupling in Fe(40 Å)/Cr(t)/Fe(40 Å) trilayers. At the right-hand side of the first antiferromagnetic peak (13 Å〈t〈16 Å), a common feature in both transport and magnetic measurements is the presence of sudden discontinuous jumps as the magnetic field is varied. By treating both transport and magnetic data on equal footing, we demonstrate that all measurements can be described by model calculations which elegantly take into account the same set of phenomenological parameters, characterizing the magnetic anisotropy, Zeeman, and bilinear and biquadratic exchange energies. Temperature-dependent FMR measurements reveal intriguing similarities between the bilinear and biquadratic coupling behaviors. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364771
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  • 6
    Electronic Resource
    Electronic Resource
    Nonlinear dynamics in microwave driven coupled magnetic multilayer systems : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6309-6311 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conventional microwave ferromagnetic resonance (FMR) techniques have proven very useful in the investigation of coupled magnetic multilayer systems. Here we show theoretically that with sufficiently high powers, a microwave magnetic field applied either parallel or perpendicular to the dc field, can drive nonlinear effects. The Landau–Lifschitz equation is used to obtain the nonlinear equations of motion for the two normal modes of a coupled two-layer system. In the usual FMR configuration, only the acoustic mode is coupled to the driving field. However, for driving fields above a critical value, energy can be transferred to the optic mode, in a process similar to the subsidiary resonance observed in spin-wave systems. At higher driving the system may display well-known transitions to chaos. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362047
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  • 7
    Electronic Resource
    Electronic Resource
    Spin-wave auto-oscillations still in need of a good model (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5624-5626 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The onset of spin-wave auto-oscillations has been studied in spheres of yttrium iron garnet pumped by a microwave field parallel or perpendicular to the dc field. Data were taken for the auto-oscillation threshold field, amplitude, and frequency as a function of sample dimension, shape, and the spin-wave relaxation rate and wave vector. The behavior near the onset confirms the theoretical prediction that the auto-oscillation results from a Hopf bifurcation. However, data for the auto-oscillation frequency and threshold field are in clear disagreement with predictions. These results indicate that although the area of nonlinear spin-wave phenomena has been under investigation for over 30 years, a good model is still needed for the auto-oscillations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345906
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  • 8
    Electronic Resource
    Electronic Resource
    Biquadratic coupling in sputtered Fe/Cr/Fe still in need of a new mechanism (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5892-5894 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The bilinear (J1) and biquadratic (J2) exchange coupling constants were measured in sputtered trilayers of (100) Fe(40 Å)/Cr(s)/Fe(40 Å) for several Cr spacer layer thicknesses in the range s=8–35 Å and as a function of temperature T, using magneto-optical Kerr effect magnetometry, Brillouin light scattering, and ferromagnetic resonance. In the samples in the range s=8–13 Å, corresponding to the first antiferromagnetic peak of J1, J2 follows J1 with a room temperature ratio J2/J1≅0.1, while in the range 25–35 Å, corresponding to the second antiferromagnetic peak, J2 also follows J1 but with a much larger ratio J2/J1≅1. This result, as well as the temperature dependence of J2 in all samples but the one with s=15 Å, cannot be explained by any of the intrinsic or extrinsic mechanisms that have been proposed for the origin of the biquadratic exchange coupling in Fe/Cr/Fe. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369905
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic properties of Ti/Fe double layers grown on MgO(100) by direct current magnetron sputtering (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4943-4945 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The purpose of this work is to investigate the magnetic properties of Ti(tTi)/Fe(104 Å) bilayers deposited by dc magnetron sputtering onto MgO(100) substrates. In-plane ferromagnetic resonance (FMR) has been used to measure the resonance field HR and linewidth ΔH as a function of the azimuthal angle and Ti layer thickness. The FMR spectra were obtained at room temperature and at a microwave frequency of 12.3 GHz. The dependence of ΔH with respect to the azimuthal angle is explained by taking into account the combined effects of intrinsic damping and angular dispersion of the cubic axes. The dependence of the magnetic relaxation on Ti thickness exhibits two different regimes. It decreases for the first Ti layers (tTi〈30 Å) and increases up to a saturation value for Ti thickness around 90 Å. Other magnetic parameters such as effective magnetization, magnetocrystalline, and perpendicular anisotropies are also discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370053
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  • 10
    Electronic Resource
    Electronic Resource
    Observation of mixed-mode oscillations in spin-wave experiments (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5086-5087 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-power ferromagnetic resonance experiments in a 1-mm-diam yttrium iron garnet sphere, driven at 8.9 GHz at room temperature, reveal evidence for a universal scenario not yet observed in this system, namely, the periodic–chaotic sequence. Well above the first-order Suhl instability threshold (P/PC∼6 dB), low-frequency (f∼200 kHz) auto-oscillations consisting of large-amplitude peaks followed by n small undulations (mixed-mode oscillations) have been observed. Both periodic and aperiodic trajectories were detected with n=1, 2, 3, and 4, which are reminiscent of the so-called homoclinic chaos. A discussion is made on the basis of a standard two-mode model. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370098
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