  We present the experimental demonstration of the parallel parametric
generation of spin-waves in a microscaled yttrium iron garnet waveguide with
nanoscale thickness. Using Brillouin light scattering microscopy, we observe
the excitation of the first and second waveguide modes generated by a stripline
microwave pumping source. Micromagnetic simulations reveal the wave vector of
the parametrically generated spin-waves. Based on analytical calculations,
which are in excellent agreement with our experiments and simulations, we prove
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. Our results pave the way for integrated
magnonics based on insulating nano-magnets.
