Abstract
We present a study of the precessional dynamics of exchange coupled Ni/sub 81/Fe/sub 19//Ni/sub 81/Fe/sub 19/:Eu/sub x/ bilayers, 50 nm thick. Eu codopants are of interest in soft ferromagnetic films since they can be used to enhance the gigahertz precessional frequency (f/sub p/) in Ni/sub 81/Fe/sub 19/ thin films without contributing to damping. Underdamped precessional dynamics with f/sub p/ "tunable" by as much as roughly 0.3 GHz were observed. Dynamical behavior agrees well with a single-domain Landau-Lifshitz simulation at constant relaxation rate /spl lambda//4/spl pi/=150 MHz across the series. The variation of precessional frequency with bias field shows that the enhancement of resonant frequency arises from an increase of dynamic anisotropy H/sub K/, matched well by static H/sub K/ as measured by SQUID. An increasing contribution in g factor (2.1-2.4) is mostly balanced by a decreasing saturation magnetization M/sub s/.
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