Determination of the magnetic damping constant in NiFe films

Sandler, G. M.; Bertram, H.N.; Silva, Thomas J.; Crawford, T. M.

doi:10.1063/1.370096

Cited by 56 publications

(21 citation statements)

References 6 publications

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“…Among these methods are frequency domain transmittance and reflectance measurements using a vector network analyzer (VNA) or time domain pulsed measurements using high-speed oscilloscopes. [1][2][3][4][5][6][7][8][9][10][11] Measuring susceptibility for low moment magnetic thin film materials, however, has historically been very challenging due to the very weak magnetic moment responses for both frequency and time domain measurement techniques. For magnetic materials with large magnetic loss tangents it is necessary to have a high signal-to-noise-ratio (SNR) for magnetic material susceptibility and resonance linewidth characterizations.…”

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confidence: 99%

A new highly sensitive broadband ferromagnetic resonance measurement system with lock-in detection

Beguhn

Zhou

Rand

et al. 2012

Journal of Applied Physics

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RF/microwave magnetic measurement systems can be categorized into broadband or narrowband systems. Narrowband systems utilize high Q cavities for magnetic material characterizations such as electron paramagnetic resonance or electron spin resonance. Example broadband characterization systems are permeameters or pulsed inductive magnetometers. Narrowband measurement systems have high sensitivity but limited bandwidth whereas broadband systems suffer from lower sensitivity. In particular, it has been challenging to precisely measure weak magnetization, high anisotropy and high ferromagnetic resonance linewidth across a broad bandwidth. In this work, we report a new highly sensitive broadband resonance measurement system with lock-in detection utilizing a broadband transmission line. The frequency of the RF source is swept while the magnetic field is fixed. The resulting curve of dP/dH versus f is similar to the dP/dH versus H curve from conventional narrowband magnetic measurement system. The imaginary component of magnetic susceptibility χ" is calculated by the equation of χ"(f)=C∫(dP/dH*dH/df)df, in which C is a constant and dH/df is determined from the Kittel equation for magnetic films. Broadband measurements of sputtered low-moment lossy NiCr (4πMs=1100 G) as well as NiFe (4πMs=11000 G) were taken and compared with conventional broadband measurement using a network analyzer.

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confidence: 99%

A new highly sensitive broadband ferromagnetic resonance measurement system with lock-in detection

Beguhn

Zhou

Rand

et al. 2012

Journal of Applied Physics

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“…In this geometry magnetostatic surface waves (MSSW) are the dominant modes, leading to qualitatively different spatiotemporal dynamics in the Py film. For the k-space calculations, the dispersion law of MSSW [16,18,19],…”

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confidence: 99%

Spin Wave Dynamics and the Determination of Intrinsic Damping in Locally Excited Permalloy Thin Films

et al. 2007

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Time-resolved scanning Kerr effect microscopy has been used to study magnetization dynamics in Permalloy thin films excited by transient magnetic pulses generated by a micrometer-scale transmission line structure. The results are consistent with magnetostatic spin wave theory and are supported by micromagnetic simulations. Magnetostatic volume and surface spin waves are measured for the same specimen using different bias field orientations and can be accurately calculated by k-space integrations over all excited plane wave components. A single damping constant of Gilbert form is sufficient to describe both scenarios. The nonuniform pulsed field plays a key role in the spin wave dynamics, with its Fourier transform serving as a weighting function for the participating modes. The intrinsic Gilbert damping parameter α is most conveniently measured when the spin waves are effectively stationary.PACS numbers: 75.30. Ds, 75.50.Bb, 75.70.Ak, 76.50.+g Interest has been growing for many years in the timedomain investigation of magnetization dynamics in response to a short magnetic pulse. An impulse excitation is broadband, but the dynamics of the magnetic system are also very sensitive to the parameters of the excitation pulse. Time-domain pulse shaping can eliminate ringing for a coherently-switched ferromagnetic element, to greatly enhance the performance for applications [1,2]. In addition, the spatial profile of the pulsed field is critical in dictating the magnetic dynamics. Magnetostatic spin waves generated by such nonuniform transient field have been observed in a number of time-resolved optical [3] and inductive [4,5] experiments, and also in frequencydomain studies [6]. The resulting position-dependent temporal response creates additional challenges for characterizing the dynamics and for determining the intrinsic magnetic damping. The focus of the present work is to address these difficulties within a simple physical framework.Under the condition of linear behavior of the spin wave dynamics in the low amplitude regime [4,5], the magnetic response is the linear superposition of all plane wave components that can be excited by the pulse. Assuming the spin waves propagate only along the x direction (the coordinate system is defined in Fig.1(a)), the out-of-plane component of magnetization can be described by: (1) where τ −1 is the inverse decay time, ω(k) is the dispersion relation, and P (k, ω(k)) is the spectral density of the pulse field determined from its spatial and temporal profiles and acts as a relative weighting factor for the different spin wave components in k-space. The influences of the pulse field parameters, the intrinsic damping, and the dispersion relation of the spin waves are contained explicitly. k c is a cut-off wave number for numerical integration (k c = 5 µm −1 is sufficient for the magnetostatic regime with the stripline dimensions used here). The initial phase angle φ is taken to be independent of frequency on account of the pulse excitation. The longer trailing edge of the pulse cau...

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“…For initial work, the net transverse magnetization response of the whole sample is determined by an inductive sampling technique [59,60]. The changing transverse magnetization gives rise to a changing flux that encircles the center conductor line and creates an electric field by Faraday's law.…”

Section: Dynamic Reversal and Large-angle Excitationmentioning

confidence: 99%

Stroboscopic Microscopy of Magnetic Dynamics

Freeman

Hiebert

Topics in Applied Physics

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Abstract. The enhanced capabilities of contemporary pulsed light sources have led to the reflourishing, in recent years, of ultrafast imaging of micromagnetic dynamics. Concurrently, interest in the subject has been intensified by other factors, such as the emergence of intrinsic magnetic response times as a potential limitation to the ultimate bandwidth of magnetic data storage and by increasingly powerful computer models of magnetic dynamics which call for experimental comparisons. This review contains a discussion of the experimental details behind ultrafast timeresolved magneto-optic imaging, sandwiched between a brief historical overview and a presentation of some recent results, and accompanied by an outline of some future prospects. Historical OverviewThe ongoing development of ultrafast laser technologies has made stroboscopic imaging of fast dynamics in microscopic structures very convenient. The stroboscopic, or "pump-probe" method as it is traditionally named by the optics community, has been grafted onto many different varieties of microscopy, including electron beam, scanning probe (force and tunneling), and, of course, optical (both conventional and near-field) [1,2,3,4]. Some applications of ultrafast optical microscopy are more fully developed than ultrafast scanning probe microscopies, many of which are still not too far beyond the "proof-of-principle" stage. This is largely because the development time for an ultrafast optical microscope is much shorter than that for combinations of ultrafast lasers with other imaging methods.Magnetic structures in particular have provided a major test bed for developments in ultrafast optical microscopy. The magneto-optic activity of ferromagnetic materials ideally suits them for this kind of experimental analysis. With characteristic relaxation times and oscillation periods ranging into the low picosecond range, and with domain wall widths and spin-wave wavelengths in the nanometer range, spatiotemporal investigation of these materials poses a difficult challenge for any type of microscopy. Ferroelectrics are another class with similar characteristics [5].As is often the case, the territory we explore now and find so fertile turns out to have been well surveyed by our predecessors, using the best tools of

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Determination of the magnetic damping constant in NiFe films

Cited by 56 publications

References 6 publications

A new highly sensitive broadband ferromagnetic resonance measurement system with lock-in detection

A new highly sensitive broadband ferromagnetic resonance measurement system with lock-in detection

Spin Wave Dynamics and the Determination of Intrinsic Damping in Locally Excited Permalloy Thin Films

Stroboscopic Microscopy of Magnetic Dynamics

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