Parametric interaction of magnetostatic waves with a nonstationary local pump

A solution is obtained for the general problem of the nonstationary interac tion of backward volume magnetostatic waves in films of yttrium-iron garnet with local parametric pumping. In the case of a large pump region, l much greater than lambda, where lambda is the wavelength of the backward volume magnetostatic waves, the problem reduces to a system of truncated equations for two packets of counter propagating waves. In the opposite case, l <lam bda, the exact problem of parametric interactions of the eigenmodes of a fe rrite film (both counterpropagating and in the same direction) is solved nu merically. Both cases are studied experimentally and good qualitative and q uantitative agreement is obtained with the theory. For the first time, the reversal of a wave front and the time reversal of the shape of backward vol ume magnetostatic wave pulses are observed and a change in the propagation time for the peak of the signal pulse and a reduction in its width owing to pumping are recorded. Two operating regimes are identified for a nonstatio nary parametric backward volume magnetostatic wave amplifier with local pum ping, which differ in the ratio of the duration of the pump pulse to the tr ansit time for the wave through the local pump region, and the effect of th e parametric excitation of two-dimensional spin waves on the interaction of backward volume magnetostatic waves with a local nonstationary parametric pump is determined. (C) 1999 American Institute of Physics. [S1063-7761(99) 02512-3].