  We employed micro-focused Brillouin light scattering to study the
amplification of the thermal spin wave eigenmodes by means of a pure spin
current, generated by the spin-Hall effect, in a transversely magnetized
Pt(4nm)/NiFe(4nm)/SiO2(5nm) layered nanowire with lateral dimensions 500x2750
nm2. The frequency and the cross section of both the center (fundamental) and
the edge spin wave modes have been measured as a function of the intensity of
the injected dc electric current. The frequency of both modes exhibits a clear
redshift while their cross section is greatly enhanced on increasing the
intensity of the injected dc. A threshold-like behavior is observed for a value
of the injected dc of 2.8 mA. Interestingly an additional mode, localized in
the central part of the nanowire, appears at higher frequency on increasing the
intensity of the injected dc above the threshold value. Micromagnetic
simulations were used to quantitatively reproduce the experimental results and
to investigate the complex non-linear dynamics induced by the spin-Hall effect,
including the modification of the spatial profile of the spin wave modes and
the appearance of the extra mode above the threshold.
