Formation of dipolar spin-wave (SW) (or magtietostatic wave) envelope solitons was observed in yttrium iron garnet films with unpinned surface spins under pulsed excitation. The solitons were formed in the spectral regions of relatively low dispersion from the short rectangular input pulses (T 4-50 ns). With the increase of the duration and/or amplitude of the input pulse, the multisoliton regime of SW propagation was registered. A theoretical interpretation of the observed nonlinear phenomena in terms of a nonlinear Schrodinger equation model with dissipation is given.(2tt/TV ) '(8'to/8k ') » to", I UI'»co, /(8to/8I UI'), (2) (3) where T is the duration of the in ut pulse, Vs 8at/8k is the wave group velocity, 8 co/8k is the wave dispersion, 8to/8IUI characterizes the wave nonlinearity, U is the dimensionless amplitude of the envelope of the propagating wave, and co"is the dissipation parameter of the propagating wave. For the case of spin-wave (SW) propagating in the ferromagnetic film (FF) the dimensionless amplitude of the SW envelope U is determined bywhere m",my are the components of the variable magnetization m and 4trMo (Mollz) is the equilibrium magnetization. The SW dissipation parameter is equal to to, 2try~k, where ) 2.8 MHz/Oe and AHk is the half-linewidth of ferromagnetic resonance in ferromagnetic film in Oe.It is worth noting that condition (3) in FF also means that the amplitude of the propagating SW should be greater than the threshold of the four-wave parametric decay process (second-order Suhl process ) toq+tol, =tot"+tot, "q;-(k;k) «k, i -1, 2, . . . , (5) which is responsible for the SW nonlinearity when the low-threshold three-wave decay processes (first-order Envelope solitons are stable nonlinear excitations that emerge during finite-amplitude wave pulse propagation in the dispersive media as a result of competition between the spreading effect of dispersion and the self-steepening effect of nonlinearity when both these effects are much stronger than the effect of dissipation. The conditions of envelope soliton formation in nonlinear dispersive media with dissipation are as follows:' (i) The Lighthill criterion which requires nonlinearity and dispersion to have opposite signs (8' N/8k')(8N/8 I UI') &0;(ii) the dissipation criteria that require the influence of dispersion and nonlinearity on the input pulse profile to be much greater than the influence of dissipation Suhl processes) COg COg, + Ng, (5a) are prohibited by conservation laws.There are two ways to satisfy the criterion (2): to find regions in the SW spectrum of the FF where dispersion 8 to/8k is sufficiently high, or to reduce the duration T of the input pulse when working in the spectral regions of relatively low dispersion.The first way was used in our work ' and led to the first experimental observation of dipole-exchange SW envelope solitons (T, 120 ns) in the regions of high dispersion near the dipole "gaps" in the dipole-exchange SW spectrum of a perpendicularly magnetized yttrium iron garnet (YIG) film with pinned sur...

The self-generation of microwave magnetic envelope solitons in magnetic films has been realized for the first time. Solitons with a width of 20 ns and a carrier frequency of 5.1555 GHz were generated for the magnetostatic backward volume wave (MSBVW) configuration in a 5.2 mm thick yttrium iron garnet film. The film and MSBVW propagation structure were part of a ring with an overall gain of 14 dB. Pulse modulation at 10 MHz provided the interrupted feedback and the active mode locking which was needed to produce a stable and continuous stream of self-generated soliton pulses. Pulse width and phase measurements confirmed the soliton nature of the self-generated pulses.[S0031-9007(98)

The end edge reflection and collision of backward volume wave bright microwave magnetic envelope solitons in long and narrow yttrium iron garnet single-crystal films has been studied experimentally. The experiments were done on 5.1-m-thick, 1-mm-wide films. The bright solitons were excited by single or double 8-36-ns-wide microwave pulses with a nominal carrier frequency of 5.8 GHz. The experiments utilized a movable transducer structure to make measurements for a range of transducer separations from 2 to 15 mm and for pulses before and after reflection. The soliton character was established from single-pulse decay versus time and distance measurements. Three decay regions were observed, a slow decay region before soliton formation, a fast decay region characteristic of solitons, and a second slow decay for linear pulses. The soliton region included both incident and reflected pulses. The exponential decay rate for the soliton regime was greater than for the linear. The soliton pulses retained the same shape and speed after edge reflection. An observed drop in pulse amplitude after passing under the pickup transducer provided a way to measure the actual power and amplitude of the soliton signal. The measured amplitudes and widths were in fair agreement with predictions for a simple sech-type order one soliton pulse. For properly timed double-pulse experiments in which a reflected lead pulse collides with the follow-on pulse before detection, the effects of soliton collisions could be examined. In the single soliton power regime, the pulses were found to retain their shape and speed after collision. At higher powers, shapes were not retained. In addition, a wake effect was observed in which the lead pulse causes a change in the detected signal for the follow-on pulse, even without collision.

The excitation of both bright and dark microwave magnetic envelope solitons has been realized for one and the same resonant ring containing a yttrium–iron–garnet film magnetostatic wave (MSW) delay line. The resonant ring modifies the MSW character to produce a series of frequency intervals with alternating regions of positive and negative dispersion. These alternating regions support bright and dark soliton production, respectively.

Microwave magnetic envelope soliton pulse trains with no decay in amplitude have been obtained in magnetic films for the first time. The solitons were formed from magnetostatic spin waves with negative dispersion, or backward volume waves, propagated in a long and narrow 5.2 mm thick yttrium iron garnet film strip biased at 1096 Oe. An interrupted feedback technique was used to produce the soliton pulse trains from an initial 25 ns wide input pulse at a carrier frequency of 5.0 GHz. The train extended for over 40 ms, 2 orders of magnitude longer than the single soliton lifetime. Measurements of the soliton width and phase profiles confirmed the soliton nature of the pulses over the entire train.