  We report room temperature electrical detection of spin injection from a
ferromagnetic insulator (YIG) into a ferromagnetic metal (Permalloy, Py).
Non-equilibrium spins with both static and precessional spin polarizations are
dynamically generated by the ferromagnetic resonance of YIG magnetization, and
electrically detected by Py as dc and ac spin currents, respectively. The dc
spin current is electrically detected via the inverse spin Hall effect of Py,
while the ac spin current is converted to a dc voltage via the spin
rectification effect of Py which is resonantly enhanced by dynamic exchange
interaction between the ac spin current and the Py magnetization. Our results
reveal a new path for developing insulator spintronics, which is distinct from
the prevalent but controversial approach of using Pt as the spin current
detector.
