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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Intrinsic damping and intentional ferromagnetic resonance broadening in thin Permalloy films

D. J. Twisselmann and R. D. McMichael

J. Appl. Phys. 93, 6903 (2003); http://dx.doi.org/10.1063/1.1543884 (3 pages) | Cited 30 times

Online Publication Date: 9 May 2003

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Detailed ferromagnetic resonance measurements on thin Ni80Fe20 films are described that determine characteristics of intrinsic damping and the effects of intentionally created defects on linewidth. Measurements are made as a function of frequency with magnetization oriented in-plane and normal to the plane. For nominally uniform films, the ferromagnetic resonance linewidth is linear in frequency for both in-plane and normal magnetization and is well described by Landau–Lifshitz damping with a constant damping parameter. The effect of inhomogeneity was investigated by depositing the Ni80Fe20 films on specially prepared substrates, one with parallel, random grooves and one with polycrystalline, antiferromagnetic NiO. The linewidth in these samples is generally larger with magnetization in-plane than it is with magnetization normal. In the NiO/Ni80Fe20 film, the in-plane linewidth is linear in frequency with a significant zero-frequency linewidth. In the Ni80Fe20 sample on the grooved substrate, the linewidth has a more complicated frequency dependence. © 2003 American Institute of Physics.
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75.50.Bb Fe and its alloys
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Gw Magnetic anisotropy

Fully controlled precessional switching of a macrospin in a cross-wire geometry

W. K. Hiebert, L. Lagae, J. Das, J. Bekaert, R. Wirix-Speetjens, and J. De Boeck

J. Appl. Phys. 93, 6906 (2003); http://dx.doi.org/10.1063/1.1543885 (3 pages) | Cited 10 times

Online Publication Date: 9 May 2003

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Ultrafast scanning Kerr microscopy measurements of half-precession-cycle, quasiballistic magnetization switching in a Permalloy™ macrospin are presented. The 20×7 μm2, 15-nm ellipse-shaped element is embedded in a continuous film of thinner Py, which effectively eliminates the remanent state closure domains and strongly increases coherence of dynamic motions in the large element. A perpendicular crossing-wire geometry allows pulse excitations to both the easy and hard axes. Data for well-terminated, ringing-suppressed ballistic switching and poorly-terminated switching with ringing are presented with hard axis pulses as small as 12 Oe and as short as ∼400-ps driving precessional switching. With addition of an easy-axis overlapping pulse, half-select precessional switching into a metastable state is observed; however, large spatial nonuniformities are introduced into the element dynamics, which ultimately defeat the half-select switching process. © 2003 American Institute of Physics.
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75.70.Kw Domain structure (including magnetic bubbles and vortices)
75.50.Bb Fe and its alloys
75.30.Ds Spin waves
75.30.Wx Spin crossover
78.20.Ls Magneto-optical effects
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Analytical solutions of Landau–Lifshitz equation for precessional switching

C. Serpico, I. D. Mayergoyz, and G. Bertotti

J. Appl. Phys. 93, 6909 (2003); http://dx.doi.org/10.1063/1.1557278 (3 pages) | Cited 28 times

Online Publication Date: 9 May 2003

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A rigorous analysis of the precessional switching dynamics in uniformly magnetized particles and films is presented. Magnetization dynamics are described by the Landau–Lifshitz equation and the precessional switching is realized by applying a field pulse orthogonal to the easy axis of the particle or the film. The analysis of the switching process is based on the explicit knowledge of two integrals of motion for the magnetization dynamics and leads to closed form analytical expressions for the magnetization in terms of Jacobi elliptic functions. It is shown that switching can occur only beyond a critical field threshold. The analytical solutions are used to predict the magnetization trajectory and the switching time under external field pulses of different amplitudes and durations. © 2003 American Institute of Physics.
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75.60.Jk Magnetization reversal mechanisms
75.50.Tt Fine-particle systems; nanocrystalline materials
75.70.Ak Magnetic properties of monolayers and thin films
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Nonlinear microscopic relaxation of uniform magnetization precession

Vladimir L. Safonov and H. Neal Bertram

J. Appl. Phys. 93, 6912 (2003); http://dx.doi.org/10.1063/1.1543891 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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Dynamic relaxation for nonlinear magnetization excitation is analyzed. For direct processes, such as magnon–electron scattering and two-magnon scattering, the relaxation rate is determined from the linear case simply by utilizing the magnetization oscillation frequency for nonlinear excitation. For an indirect process, such as slow-relaxing impurities, the analysis gives an additional relaxation term proportional to the excitation level. In all cases the effective magnetization damping is increased compared to Landau–Lifshitz–Gilbert damping. © 2003 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Ds Spin waves
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)
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