209 research outputs found
Interference of coherent spin waves in micron-sized ferromagnetic waveguides
We present experimental observations of the interference of spin-wave modes
propagating in opposite directions in micron-sized NiFe-waveguides. To monitor
the local spin-wave intensity distribution and phase of the formed interference
pattern, we use Brillouin light scattering microscopy. The two-dimensional
spin-wave intensity map can be understood by considering the interference of
several waveguide eigenmodes with different wavevectors quantized across the
width of the stripe. The phase shows a transition from linear dependence on the
space coordinate near the antennas characteristic for propagating waves to
discrete values in the center region characteristic for standing waves
Non-resonant wave front reversal of spin waves used for microwave signal processing
It is demonstrated that non-resonant wave front reversal (WFR) of spin-wave
pulses caused by pulsed parametric pumping can be effectively used for
microwave signal processing. When the frequency band of signal amplification by
pumping is narrower than the spectral width of the signal, the non-resonant WFR
can be used for the analysis of the signal spectrum. In the opposite case the
non-resonant WFR can be used for active (with amplification) filtering of the
input signal.Comment: 4 pages, 3 figure
Field-induced transition from parallel to perpendicular parametric pumping for a microstrip transducer
Microstrip transducers used for the excitation of spin waves in magnetic
films possess two characteristic properties: high spatial localization of the
microwave magnetic field and the presence of field components parallel and
perpendicular to the bias field.
Here, the effects of these features on the process of parametric pumping are
presented. By microwave measurements of the spin-wave instability threshold a
transition from parallel pumping to perpendicular pumping at the critical field
with the minimal threshold is observed. This transition is
accompanied by a sharp threshold increase above the critical field due to the
spatial confinement of the pump region.Comment: 4 pages, 2 figure
Dispersion Characteristics of Spin-Electromagnetic Waves in Planar Multiferroic Structures with Coplanar Transmission Line
Introduction. The distinctive feature of a coplanar transmission line with thin ferrite and ferroelectric films is the absence of undesirable irregularities in dispersion for relatively low frequencies when the wavelength approaches the thickness of ferroelectric layer, in contrast to the open ferrite-ferroelectric wave-guiding structure without metallization.Aim. The purpose of this paper is twofold: (i) to develop a theory of the wave spectra in the multiferroic structures based on the coplanar lines; (ii) using this theory to find ways to enhance the electric tuning range.Materials and methods. The dispersion relation for spin-electromagnetic waves was derived through analytical solution of the full set of the Maxwell's equations utilizing a method of approximate boundary conditions.Results. A theory of spin-electromagnetic wave spectrum has been developed for the thin-film ferrite-ferroelectric structure based on a coplanar transmission line. According to this theory, dispersion characteristics of the spin-electromagnetic waves were described and analyzed for different parameters of the structure. The obtained results show that the investigated structure demonstrates a dual electric and magnetic field tunability of wave spectra. Its efficiency increases with an increase in the thicknesses of the ferrite and ferroelectric films and with a decrease in the width of the central metal strip.Conclusion. The distinctive features of the proposed coplanar waveguides are the thin-film planar topology and dual tunability of the wave spectra. All these advantages make the proposed structures perspective for development of new microwave devices.Introduction. The distinctive feature of a coplanar transmission line with thin ferrite and ferroelectric films is the absence of undesirable irregularities in dispersion for relatively low frequencies when the wavelength approaches the thickness of ferroelectric layer, in contrast to the open ferrite-ferroelectric wave-guiding structure without metallization.Aim. The purpose of this paper is twofold: (i) to develop a theory of the wave spectra in the multiferroic structures based on the coplanar lines; (ii) using this theory to find ways to enhance the electric tuning range.Materials and methods. The dispersion relation for spin-electromagnetic waves was derived through analytical solution of the full set of the Maxwell's equations utilizing a method of approximate boundary conditions.Results. A theory of spin-electromagnetic wave spectrum has been developed for the thin-film ferrite-ferroelectric structure based on a coplanar transmission line. According to this theory, dispersion characteristics of the spin-electromagnetic waves were described and analyzed for different parameters of the structure. The obtained results show that the investigated structure demonstrates a dual electric and magnetic field tunability of wave spectra. Its efficiency increases with an increase in the thicknesses of the ferrite and ferroelectric films and with a decrease in the width of the central metal strip.Conclusion. The distinctive features of the proposed coplanar waveguides are the thin-film planar topology and dual tunability of the wave spectra. All these advantages make the proposed structures perspective for development of new microwave devices
Generation of spin-wave dark solitons with phase engineering
We generate experimentally spin-wave envelope dark solitons from rectangular
high-frequency dark input pulses with externally introduced phase shifts in
yttrium-iron garnet magnetic fims. We observe the generation of both odd and
even numbers of magnetic dark solitons when the external phase shift varies.
The experimental results are in a good qualitative agreement with the theory of
the dark-soliton generation in magnetic films developed earlier [Phys. Rev.
Lett. 82, 2583 (1999)].Comment: 6 pages, including 7 figures, submitted to Phys. Rev.
Formation of Random Dark Envelope Solitons from Incoherent Waves
This letter reports experimental results on a new type of soliton: the random
temporal dark soliton. One excites an incoherent large-amplitude propagating
spin-wave packet in a ferromagnetic film strip with a repulsive, instantaneous
nonlinearity. One then observes the random formation of dark solitons from this
wave packet. The solitons appear randomly in time and in position relative to
the entire wave packet. They can be gray or black. For wide and/or very strong
spin-wave packets, one also observes multiple dark solitons. In spite of the
randomness of the initial wave packets and the random formation processes, the
solitons show signatures that are found for conventional coherent dark
solitons.Comment: 10 pages, 4 figures, double-spaced preprint forma
Theory for a dissipative droplet soliton excited by a spin torque nanocontact
A novel type of solitary wave is predicted to form in spin torque oscillators
when the free layer has a sufficiently large perpendicular anisotropy. In this
structure, which is a dissipative version of the conservative droplet soliton
originally studied in 1977 by Ivanov and Kosevich, spin torque counteracts the
damping that would otherwise destroy the mode. Asymptotic methods are used to
derive conditions on perpendicular anisotropy strength and applied current
under which a dissipative droplet can be nucleated and sustained. Numerical
methods are used to confirm the stability of the droplet against various
perturbations that are likely in experiments, including tilting of the applied
field, non-zero spin torque asymmetry, and non-trivial Oersted fields. Under
certain conditions, the droplet experiences a drift instability in which it
propagates away from the nanocontact and is then destroyed by damping.Comment: 15 pages, 12 figure
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