Finite size effects on spin-torque driven ferromagnetic resonance in spin-valves with a Co/Ni synthetic free layer

摘要

Spin-torque driven ferromagnetic resonance (ST-FMR) is used to study magneticexcitations in Co/Ni synthetic layers confined in nanojunctions. Field sweptST-FMR measurements were conducted with a magnetic field applied perpendicularto the layer surface. The resonance lines were measured under low amplitudeexcitation in a linear response regime. The resulting resonance fields werecompared with those obtained using conventional rf field driven FMR on extendedfilms with the same Co/Ni layer structure. A lower resonance field is found inconfined structures. The effect of both dipolar fields acting on the Co/Nilayer emanating from other magnetic layers in the device and finite sizeeffects on the spin wave spectrum are discussed.