Morteza Mohseni, Martin Kewenig, Roman Verba, Qi Wang, Michael Schneider, Björn Heinz, Felix Kohl, Carsten Dubs, Bert Lägel, Alexander A. Serga, Burkard Hillebrands, Andrii V. Chumak, Philipp Pirro

• Herein, experimental demonstration of the parallel parametric generation of spin waves in a microscaled yttrium iron garnet waveguide with nanoscale thickness is presented. Using Brillouin light scattering microscopy, the parametric excitation of the first and second waveguide modes by a stripline microwave pumping source is observed. Micromagnetic simulations reveal the wave vector of the parametrically generated spin waves. Based on analytical calculations, which are in excellent agreement with experiments and simulations, it is proved that the spin-wave radiation losses are the determinative term of the parametric instability threshold in this miniaturized system. The used method enables the direct excitation and amplification of nanometer spin waves dominated by exchange interactions. The presented results pave the way for integrated magnonics based on insulating nanomagnets.