  This work provides a detailed investigation of the measured in-plane
field-swept homodyne-detected ferromagnetic resonance (FMR) spectra of an
extended Co/Cu/NiFe pseudo spin valve stack using a nanocontact (NC) geometry.
The magnetodynamics are generated by a pulse-modulated microwave current and
the resulting rectified dc mixing voltage, which appears across the NC at
resonance, is detected using a lock-in amplifier. Most notably, we find that
the measured spectra of the NiFe layer are composite in nature and highly
asymmetric, consistent with the broadband excitation of multiple modes.
Additionally, the data must be fit with two Lorentzian functions in order to
extract a reasonable value for the Gilbert damping of the NiFe. Aided by
micromagnetic simulations, we conclude that (i) for in-plane fields the rf
Oersted field in the vicinity of the NC plays the dominant role in generating
the observed spectra, (ii) in addition to the FMR mode, exchange dominated spin
waves are also generated, and (iii) the NC diameter sets the mean wavevector of
the exchange dominated spin wave, in good agreement with the dispersion
relation.
