Backward-volume-wave microwave-envelope solitons in yttrium iron garnet films

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Abstract
Microwave-magnetic-envelope (MME) solitons generated from nonlinear magnetostatic-backward-volume wave packets have been observed in magnetic thin films. The MME signals were excited by 5–50-ns wide microwave pulses at 5.8 GHz in a 15-mm-long by 2.5-mm-wide, 7.2-μm-thick single-crystal yttrium iron garnet (YIG) film strip magnetized in plane and parallel to the long side of the strip. The wave packets were propagated parallel to the static field. The wave packets were launched and the propagating MME pulse signals were detected with planar microstrip transducers 4 mm apart. Envelope soliton behavior was evident from the time-resolved wave forms observed for various input power and pulse width combinations. At low power levels, one sees a relatively broad output pulse which scales with the width of the input pulse and a peak power which increases linearly with the input power. As the input power is increased above some threshold in the 0.5–1-W range, output pulses show a narrowing and steepening which is characteristic of microwave-magnetic-envelope solitons. Further increases in input power produce multiple-peak profiles, characteristic of multiple soliton generation. The experimental results are consistent with the various characteristic times for linear and nonlinear MME pulse propagation and soliton formation. However, numerical modeling based on the magnetic form of the nonlinear Schrödinger equation with initial conditions and parameters which match the experiments yields calculated profiles which show soliton effects but do not quantitatively match the experimental results.