Suppression of Spin-Orbit Torque Switching by the Magnetic Proximity Effect

Functional magnetic multilayers are particularly interesting for enabling many emerging spintronic physics, including spin-orbit torque (SOT), magnetic proximity effect (MPE), and perpendicular magnetic anisotropy (PMA), among many others. A comprehension of these spintronic phenomena is vital for the development of advanced spintronic materials and devices. Here, we investigate the interplay between the MPE and the current-induced SOT switching in the perpendicularly magnetized Pt/[Co/Pd]_K multilayers (with K being the number of repetitions). In particular, we find evidence of the MPE-induced magnetism in the [Co/Pd]₉ multilayers by revealing the boosted saturation magnetization (M_s) from 1400 to 2450 emu/cc. By conducting a current-induced SOT switching experiment in these multilayers, we observe a substantial suppression of the SOT switching ratio. The underlying physics is attributed to the rapid spin relaxation of spin current in the MPE-magnetized Pd layer, which prohibits an efficient diffusion of spin currents along the thickness direction of the [Co/Pd]₉ multilayers, as suggested by first-principles calculations. Our work could help to clarify the controversial interplay between the MPE and the SOT switching, which could be useful for designing functional magnetic multilayers for enabling efficient spin-orbitronics.