Chaos and automodulation of magnetostatic waves (MSW)

Abstract

of Sciences of the USSR, Saratov Branch, Saratov / 410720 USSR Routes to chaos and automodulation under nonlinear MSW propagation in epitaxial films and monocrystall slabs of YIG were investigated.In the r? ion of the first-order Suhl instability ( Fig.1) of surface MSW ?MSSW) chaotic spectra with properties and magnetic field (H) dependence similar 50 that of the case kinetic instability of parametric spin waves 93was observed. Chaotic spectra have maximum intensity at the double FMR frequency 2fH, fH=Hi, (4% M O <3H<61M0) and frequency interval Af=2f +f, f -MSS'VV frequency, f>2fIf Af was small the prechaotic s ectra had satellites which bgiadened with increased MSSN power t P) and disappeared with chaotic spectra created there after. For frequency f near upper MSSW frequency band f -f +2mM0, so the bf was larger (f -fc d f) route to chaos w& gbserved without any selfoscillatfons in prechaotic motion. Analogous chaotic spectra but only for smalldf in the first-order Suhl instability of forward volume MSW (FVMSW) were observed (3H<165MO, f -x(H-49 M?)).In the region of second-order Suhl instabilia; of FVMSrV (f € f ( 2 f ) universal period-doubling bifurcation and distruction 8f two-Yrequency qwasiperiodic motion routes to chaos were observed (Fig.2). More obviously these routes were observed in region of high dispersion. Based on nonlinear Schrodinger equation with dissipation the development of FVMSW modulation instability was investigated. Possibility of period-doubling bifuscation and distruction of quasiperiodic motion routes to chaos shown. Fig.1. Creation of MSW noise spectra vs input power A) MSSW, (111) film, 5 mkm, H,=600 Oe, Pth=l.5 mW B) MFW, ( 1 1 0 ) plate, 40 mkm, H0=1970 Oe,Pth=1.2 mW I

Nonlinear dynamics of modulation instability in distributed resonators under external harmonic driving

“…All the results presented below are obtained in the case where the maximum achievable amplitude of stationary oscillations in the resonator, which is determined from Eq. (12), is smaller than this value.…”

“…At the same time, considering spatially bounded systems with allowance for an external source and the dissipation is also of interest. Earlier, the occurrence of self-modulation (i. e., the appearance of new spectral components incommensurate with the input-signal frequency) and transition to chaos during the MI development were considered in some papers (see, e. g., [11][12][13][14]), both theoretically and numerically. Note that these papers were devoted to an analysis of magnetostatic waves in ferrite films, but since the nonlinear Schrödinger equation (NLS)…”

A Tunable Microwave Source using Nonlinear Magnetostatic Surface Waves in Magnetic Garnet Films

“…The external magnetic field is 10000e. For a cw MSSW, onset of modulation instability [8] requires that the frequency shift characterized by a dispersion parameter a2a / d k 2 , and the frequency shift characterized by a nonlinear parameter ?a / al+lZ must have opposite signs, where o, k, 141 are the MSSW angular frequency, wave number and amplitude, respectively. Once this sign condition (i.e., Lighthill condition [6]) is satisfied and the MSSW power is beyond a threshold for the modulation instability, the traveling MSSW envelope will be modulated with a frequencyf, which can be derived from the nonlinear Schriidinger equation as:…”

Theory of Nonlinear Ferromagnetic Resonance in the Samples with Magnetostatic and Exchange Boundary Conditions Imposed

“…The 1st order and parallel pumping instability of the Walker magnetostatic modes in a sphere [31] was discussed in [4,30] and in a thin, axially magnetized cylinder in [34]. But very interesting results, especially in the study of auto-oscillations and chaos, were obtained in the main resonance (2nd order) instability configuration [15,17].…”

“…They were performed either as conventional resonance experiments (the sample placed in a cavity), or, especially these reported in the Russian literature, with the rf power provided by a thin metallic antenna, stuck at the sample surface. They included measurements of the Suhl threshold [9][10][11][12][13][14] and investigation of the time-dependent nonlinear phenomena [15][16][17][18][19][20][21]. In a thin slab, the spin-wave approximation loses its validity, because the wavelength of the excited dipole-exchange and magnetostatic modes (tue modes of the -sample) may be comparable with the sample thickness and the boundary conditions become important, what makes the calculation difficult.…”