Gilbert Damping in Single and Multilayer Ultrathin Films: Role of Interfaces in Nonlocal Spin Dynamics

Abstract

Unique features of the Gilbert damping in magnetic multilayers were investigated by ferromagnetic resonance (FMR) using magnetic single and double layer structures prepared by molecular beam epitaxy. The FMR linewidth for the Fe films in the double layer structures was larger than the FMR linewidth in the single Fe films having the same thickness. The additional FMR linewidth scaled inversely with the film thickness, and increased linearly with increasing microwave frequency. These results demonstrate that a transfer of electron angular momentum between the magnetic layers leads to additional relaxation torques.

Detection of microwave phase variation in nanometre-scale magnetic heterostructures

“…Known sources of timedependent effective fields include interlayer coupling: either magnetostatic/Neel, or dynamical/spin pumping 26 . Neither type of coupling will reproduce the phase offset observed and coupling has been neglected in the simulation.…”

Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers

“…In case of Gilbert damping, ⌬H depends linearly on the microwave angular frequency f , i.e., ⌬H = ␣ ef f f / ␥ g . The difference in the damping parameter, determined by the FMR linewidth, for samples without capping layer and samples in which the capping N layer is sufficiently thick to fully dissipate the pumped magnetic moment, is attributed to the loss of spin momentum in Py due to relaxation of the spin accumulation in N. This permits the determination of the additional interface damping due to spin pumping, 27 which in turn fixes the interfacial spin-mixing conductance to…”

Electrical detection of spin pumping: dc voltage generated by ferromagnetic resonance at ferromagnet/nonmagnet contact

“…This has been observed experimentally in nanopillar structures. [13][14][15][16][17] The total spin current is given by I s pump . The opposite regime is when the spin-flip relaxation rate is smaller than the spin injection rate.…”

“…Recently, spin pumping has been demonstrated in ferromagnetic resonance experiments with thin multilayers, where it appears as an enhancement of the Gilbert damping constant of magnetization dynamics, [13][14][15][16][17] and using time resolved magneto-optic Kerr effect. 18 Although these experiments are very important in providing evidence for the spin pumping mechanism, the detection technique can be viewed as an indirect method to measure the spin pumping effect.…”