  Photoexcitation and shaping of a propagating surface plasmon polariton (SPP)
on silver and gold microstructures are well established and lead to the
discovery of the plasmonic spin-Hall effect recently. Whereas silver is often
the material of choice due to its exceptional low plasma frequency and weak
damping, similar observations have not been reported for ferromagnetic metals.
In this work, we report on propagating SPPs on Ni$_{80}$Fe$_{20}$
microstructures imaged by photoemission electron microscopy (PEEM) in
combination with a tunable femtosecond laser system at MHz repetition rate.
Circular dichroic (CD) images in threshold PEEM show clear edge-induced SPPs
with sub-micrometer wavelength and propagation length of about 3.5 $\mu$m.
Analysis of the interference patterns as well as the coupling of the optical
spin angular momentum to the observed fringe fields reveal propagation
characteristics exclusive to evanescent waves and the presence of the plasmonic
spin-Hall effect. Our work provides direct evidence that many materials with a
high plasma frequency allow for excitation and observation of propagating SPPs
at the dielectric/metal interface via CD PEEM imaging, enabling
magnetoplasmonic investigation of common ferromagnets on nanometer length and
femtosecond time scales.
