We present the experimental observation of localized parallel parametric generation of spin waves in a transversally in-plane magnetized Ni81Fe19 magnonic waveguide. The localization is realized by combining the threshold character of parametric generation with a spatially confined enhancement of the amplifying microwave field. The latter is achieved by modulating the width of the microstrip transmission line which is used to provide the pumping field. By employing microfocussed Brillouin light scattering spectroscopy, we analyze the spatial distribution of the generated spin waves and compare it with numerical calculations of the field distribution along the Ni81Fe19 waveguide. This provides a local spin-wave excitation in transversally in-plane magnetized waveguides for a wide wave-vector range which is not restricted by the size of the generation area.
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As the wavelength of the used microwaves exceeds the size of the investigated microstructure by orders of magnitude, no difference between a simulation for fp = 12 GHz and fp = 14 GHz is to be expected. The performance of a continuous wave simulation is valid since the lengths of the applied pulses exceed the oscillation period by orders of magnitude.
The largest value of follows from the comparison of Fig. 2(b) with the dispersion relation of spin waves in a thin film with Ms = 600 kA/m for , where is identified with the point of maximal excitation at (see text). The demagnetization field in the center of the waveguide was determined to following the approach in Ref. 18.