  The recently discovered spin Hall magnetoresistance effect electrically
probes pure spin current flow across a ferrimagnetic insulator/normal metal
bilayer interface. While usually the DC electrical resistance of the bilayer is
measured as a function of the magnetization orientation in the magnetic
insulator, we here present magnetoimpedance measurements using bias currents
with frequencies up to several GHz. We find that the spin Hall
magnetoresistance effect persists up to frequencies of at least 4 GHz, enabling
a fast readout of the magnetization direction in magnetic insulator/normal
metal bilayers. Our data furthermore show that all interaction time constants
relevant for the spin Hall magnetoresistance effect are shorter than 40 ps.
