  We experimentally image the magnetic precession phase of patterned spin Hall
multilayer samples to study the rf driving field vector using time-resolved
anomalous Nernst effect (TRANE) microscopy. Our ferromagnetic resonance (FMR)
measurements quantify the phase and amplitude for both the magnetic precession
and the electric current, which allows us to establish the total driving field
orientation and the strength of spin Hall effect. In a channel of uniform
width, we observe spatial variation of the FMR phase laterally across the
channel. We interpret our findings in the context of electrical measurement
using the spin-transfer torque ferromagnetic resonance technique and show that
observed phase variation introduces a systematic correction into the spin Hall
angle if spatial phase and amplitude variations are not taken into account.
