Precessional dynamics and damping in Co/Cu/Py spin valves

Abstract

We have studied the precessional dynamics of Co/Cu/Py (where Py = Ni81Fe19) trilayers by time-resolved x-ray resonant magnetic scattering at the synchrotron radiation facility BESSY II. We have found that the magnetic precessional decay time of Fe magnetic moments in Py layers decreases when changing the mutual orientation of the magnetization direction of Py and Co layers from parallel to antiparallel. The observed changes of the decay time can be associated with the spin pumping induced damping effect.

ALICE—An advanced reflectometer for static and dynamic experiments in magnetism at synchrotron radiation facilities

“…This has been taken as a clear signature for a spin pumping effect. 77 In case of Co 2 MnGe/Au/Py trilayers, evidence was found for the excitation of two magnon scattering, which is expressed in sudden shift of the precessional phase without a change of frequency. The two magnon scattering in the Py film is only observed when the Co 2 MnGe Heusler layer is in a domain state, generating inhomogeneous stray fields from the domain walls.…”

“…87 The ability of TR-XRMS to probe element specific free precessional magnetization dynamics allows studies of artificially prepared complex structures with more than one magnetic material. We have studied the free precessional dynamics of the Fe magnetic moments in Ni 81 Fe 19 alloy films (Py), 75 in spin valve type trilayers such as Co/Cu/Py, Co 2 MnGe/V/Py and Co 2 MnGe/Au/Py, 77,78,88 or Py/Cu and Py/AlO multilayer structures. 76 An interesting effect has been found by studying magnetization precessional dynamics of Py layers in the Co/Cu/Py spin valves having two different configurations of mutual orientation of magnetization in Py and Co layers: parallel (P) and antiparallel (AP).…”

“…Another transient state can be excited that changes the direction of the magnetization after field pulse excitation, followed by a damped precessional motion about the new field direction. [74][75][76][77][78] Implementation of time-resolved XRMS (TR-XRMS) for probing the transverse magnetization dynamics has the advantages of being element specific and sensitive to layer thickness and interfaces, which is particularly advantageous for investigations of magnetic heterostructures. It should also be mentioned that similar methods have been developed for studying the magnetization dynamics on the picosecond time scale, including the use of microwave excitations phase-locked with photon bunch frequency.…”

Dynamic exchange via spin currents in acoustic and optical modes of ferromagnetic resonance in spin-valve structures

“…[ 19 ]. Probably this effect was observed in several papers [ [20][21][22] ]. However, its interpretation in these papers fully ignores the hybridization of resonance modes, and therefore it is hard to draw some clear conclusions.…”

“…From this point of view, the difference of damping for the acoustic and optical modes in a FM/NM/FM trilayer as a result of a dynamic spin currents exchange, theoretically predicted by Kim and Chappert [ 19 ], seems to be experimentally unachievable. Nevertheless, in several recent papers [20][21][22] experimental observations of this effect have been already claimed. There is, however, a full ignorance of the fact that the FMR peaks hybridization will also influence the linewidth even if a separate measurement of the precession in each layer can be done.…”