Electrical detection of multiple ferromagnetic resonance modes in interlayer exchange coupled Fe_(20)Ni_(80)/Ru/Fe_(20)Ni_(80) multilayers

摘要

We report the electrical detection of multiple ferromagnetic (FM) resonance modes in multilayers of Pt/Fe20Ni80/Ru/Fe20Ni80 using microwave spin pumping and the inverse spin Hall effect (ISHE) as a function of Ru layer thickness t(Ru). The electrically detected voltage signals were analyzed for the anti-parallel magnetization state as well as the "spin-flop" magnetization state of the two Fe20Ni80 layers. When the two FM layers are antiferromagnetically (AFM) coupled (t(Ru) = 1 nm), both the optic and acoustic modes were observed. The amplitude of the acoustic mode voltage signals obtained increases with frequency. However, when the two magnetic layers are ferromagnetically coupled (t(Ru) = 1.4 nm), only acoustic mode was observed whose voltage signals decreases as frequency increases. We demonstrate the tunability of the sign of the ISHE voltage in the AFM coupled system by controlling the polarization of the spin currents.