In-plane spin-orbit torque magnetization switching and its detection using the spin rectification effect at subgigahertz frequencies

In-plane magnetization reversal of a permalloy/platinum bilayer was detected using the spin rectification effect. Using a subgigahertz microwave frequency to excite spin-torque ferromagnetic resonance (ST-FMR) in the bilayer induces two discrete DC voltages around an external static magnetic field of 0 mT. These discrete voltages depend on the magnetization directions of the permalloy and enable detection of the in-plane magnetization reversal. The threshold current density for the magnetization reversal is around $10--20\phantom{\rule{0.16em}{0ex}}\mathrm{MA}/\mathrm{c}{\mathrm{m}}²$, the same order as for known spin-orbit torque switching with in-plane magnetization materials. The magnitude of the signal is the same or larger than that of the typical ST-FMR signal; that is, detection of magnetization switching is highly sensitive in spite of deviation from the optimal ST-FMR condition. The proposed method is applicable to a simple device structure even for a small ferromagnetic electrode with a width of 100 nm.