Magnon transport controlled by local parametric excitation
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We report that magnetostatic magnon transport can be controlled by local parametric excitation of short-wavelength magnons. We found that the parametrically excited magnon either enhances or suppresses the traveling magnetostatic magnons, depending on the frequency of the magnetostatic magnons. Our time-domain measurements of the magnon transport show that the change in the static magnetization due to the creation of the parametrically excited magnons is responsible for the control of the magnetostatic magnon transport. This result provides insight into magnon-based devices without complex microprocessing.Keywords:
Magnon
Spin wave
According to the dispersion relation of ferromagnetic granular film from spin wave excitation and spin-polarized excitation, taking the Fe-SiO2 granular film as a case, the spin wave excitation spectrum is independent of temperature, but the spin-polarized excitation dispersion spectrum is dependent of;and both increase with the wave vector increasing which is discontinuous. It hasn't the periodicity of the spin wave excitation dispersion spectrum of mass crystal.
Spin wave
Dispersion relation
Wave vector
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Spin-wave amplification techniques are key to the realization of magnon-based computing concepts. We introduce a novel mechanism to amplify spin waves in magnonic nanostructures. Using the technique of rapid cooling, we create a non-equilibrium state in excess of high-energy magnons and demonstrate the stimulated amplification of an externally seeded, propagating spin wave. Using an extended kinetic model, we qualitatively show that the amplification is mediated by an effective energy flux of high energy magnons into the low energy propagating mode, driven by a non-equilibrium magnon distribution.
Magnon
Spin wave
Realization (probability)
Energy flux
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Conditions for the appearance of the three, four, and five magnon fusions have been derived by Gottlieb and Suhl by making use of the dispersion relation of the spin wave, restricted to the Zeeman and exchange terms. In this paper we have determined these conditions of existence from the correct relations of dispersion containing the dipolar term neglected in the previous calculations. Experimental studies of the transient growth of parallel-pumped spin waves are in good agreement with these theoretical results, thus verifying that the parametric magnons are propagating perpendiculary to the dc magnetic field as predicted by the theory of Sparks and Kittel.
Magnon
Dispersion relation
Spin wave
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Determining the spin wave exchange constant of ferromagnets using canted high-order exchange magnons
We propose an alternative method for obtaining the spin wave exchange constant of a ferromagnetic material. This involves generating and detecting canted high-order magnons in Co films using a time-resolved magneto-optical Kerr effect instrument, which enables the extraction of the spin wave exchange constant in a single film thickness in a reliable manner. To enhance the sensitivity of high-order magnon detection, we perform simultaneous measurements of differential Kerr rotation and ellipticity on both sides of the film. This method will be particularly useful in practical situations where the magnetic properties of a material vary with thickness or where it is not feasible to produce films of the same quality.
Magnon
Spin wave
Constant (computer programming)
Magnonics
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The impact of the longitudinal spin Seebeck effect (LSSE) on the magnon damping in magnetic-insulator/nonmagnetic-metal bilayers was recently discussed in several reports. However, results of those experiments can be blurred by multimode excitation within the measured linewidth. In order to avoid possible intermodal interference, we investigated the damping of a single magnon group in a platinum covered yttrium iron garnet (YIG) film by measurement of the threshold of its parametric excitation. Both dipolar and exchange spin-wave branches were probed. It turned out that the LSSE-related modification of spin-wave damping in a micrometer-thick YIG film is too weak to be observed in the entire range of experimentally accessible wave vectors. At the same time, the change in the absolute temperature of the YIG layer, which can appear by applying a temperature gradient, strongly modifies the damping value.
Yttrium Iron Garnet
Magnon
Spin wave
Magnetic damping
Magnonics
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Spin-wave amplification techniques are key to the realization of magnon-based computing concepts. We introduce a novel mechanism to amplify spin waves in magnonic nanostructures. Using the technique of rapid cooling, we create a nonequilibrium state in excess of high-energy magnons and demonstrate the stimulated amplification of an externally seeded, propagating spin wave. Using an extended kinetic model, we qualitatively show that the amplification is mediated by an effective energy flux of high energy magnons into the low energy propagating mode, driven by a nonequilibrium magnon distribution.
Magnon
Spin wave
Realization (probability)
Energy flux
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It is predicted that in 2D magnonic crystals the edge rotational magnons of forward volume magnetostatic spin waves can exist. Under certain conditions, locally bounded magnons may appear within the crystal consisting of the ferromagnetic matrix and periodically inserted magnetic/non-magnetic inclusions. It is also shown that interplay of different resonances in 2D magnonic crystal may provide conditions for spin wave modes existence with negative group velocity.
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Crystal (programming language)
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The magnetic excitations in ferromagnetic SrRuO$_3$ were studied by inelastic neutron scattering combining experiments on triple-axis and time-of-flight spectrometers with and without polarization analysis. A quadratic spin-wave dispersion with an anisotropy gap describes the low-energy low-temperature response. The magnon dispersion extends to at least 35 meV and there is no direct evidence for a continuum of Stoner excitations below this energy. However, the magnon response is weakened at higher energy. In addition to the anomalous softening of the spin-wave stiffness and of the gap, which is induced by the topology of the Bloch states, the magnon excitations are broadened in energy and this effect increases upon heating.
Magnon
Spin wave
Dispersion relation
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Spin-wave interactions in ferromagnetic insulators have a well-established theoretical foundation, in contrast to the situation for antiferromagnets. These interactions may be classified into two groups according to whether the dominant aspects are of one- or two-magnon character. The weak interactions between spin waves excited at low temperatures are responsible for the success of "free" (or noninteracting) spin-wave calculations in explaining low-temperature thermodynamic properties. In contrast, the two-magnon aspects appear in connection with two-magnon Raman scattering, where pairs of magnons are created in close proximity and consequently interact strongly. Parallels with analogous systems, especially antiferromagnetic spin waves and phonons, are noted in reviewing the ferromagnetic case. Emphasis is placed on the structure of the theory, rather than on the wealth of experimental activity.
Magnon
Spin wave
Heisenberg model
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We present a joint experimental and theoretical study of parametric resonance of spin wave eigenmodes in Ni$_{80}$Fe$_{20}$/Pt bilayer nanowires. Using electrically detected magnetic resonance, we measure the spectrum of spin wave eigenmodes in transversely magnetized nanowires and study parametric excitation of these eigenmodes by a microwave magnetic field. We also develop an analytical theory of spin wave eigenmodes and their parametric excitation in the nanowire geometry that takes into account magnetic dilution at the nanowire edges. We measure tuning of the parametric resonance threshold by antidamping spin Hall torque from a direct current for the edge and bulk eigenmodes, which allows us to independently evaluate frequency, damping and ellipticity of the modes. We find good agreement between theory and experiment for parametric resonance of the bulk eigenmodes but significant discrepancies arise for the edge modes. The data reveals that ellipticity of the edge modes is significantly lower than expected, which can be attributed to strong modification of magnetism at the nanowire edges. Our work demonstrates that parametric resonance of spin wave eigenmodes is a sensitive probe of magnetic properties at edges of thin-film nanomagnets.
Spin wave
Spin pumping
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