Exploration of precessional spin dynamics in magnetic multilayers

In this article, we present magnetization dynamics studies on magnetic multilayers using time resolved resonant magnetic x-ray scattering, which accesses both the frequency and the damping of the free magnetization precession. Here, we compare two multilayers with ferromagnetic Py (Py=Ni0.8Fe0.2) layers separated by conducting Cu layers and by non-conducting AlOx layers. Magnetic Bragg peaks from the multilayer are excited by tuning the circular polarized x-ray energy to the L-2,L-3 resonant absorption edges of Fe and Ni in Py. The coherent precessional dynamics follows then from an analysis of the time dependent Bragg peak intensity after field pulse excitation. We find coherent precession of all magnetic layers within both multilayers and also the same precessional frequency, independent of the interlayer material. At the same time, the precessional damping is considerably different for Cu and AlOx as interlayer materials. Reasons for the enhanced damping in Py/Cu multilayers are discussed. Additional depth dependent studies are presented using a single Py layer through variation of the angle of incidence. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4766453]