  We report results of micro-Brillouin-Mandelstam light scattering spectroscopy
of thermal magnons in the two-phase synthetic multiferroic structure consisting
of a piezoelectric (PMN-PT) substrate and a Ni thin film with the thickness of
64 nm. The experimental data reveal the first two modes of the perpendicular
standing spin waves (PSSW) spatially confined across the Ni thin film. A
theoretical analysis of the frequency dependence of the PSSW peaks on the
external magnetic field reveals the asymmetric boundary condition, i.e.
pinning, for variable magnetization at different surfaces of the Ni thin film.
The strain field induced by applying DC voltage to PMN-PT substrate leads to a
down shift of PSSW mode frequency owing to the magneto-elastic effect in Ni,
and corresponding changes in the spin wave resonance conditions. The observed
non-monotonic dependence of the PSSW frequency on DC voltage is related to an
abrupt change of the pinning parameter at certain values of the voltage. The
obtained results are important for understanding the thermal magnon spectrum in
ferromagnetic films and development of the low-power spin-wave devices.
