Magnetization relaxation and structure of CoFeGe alloys

摘要

The magnetic relaxation of 10 and 50 nm thin films of (CoFe)_(100-x)Ge_x (0 at. %≤35 at. %) alloys was investigated by broadband ferromagnetic resonance (FMR) experiments. 10 nm thin films exhibit a significant two magnon contribution to the FMR linewidth. The 50 nm films exhibit very low damping constants of α ≈0.0025 and relaxation rates as low as 33 MHz in the composition range of 20 at. %≤x≤30 at. % Ge after annealing. Structural characterization revealed B2 order for these compositions. First principles calculations confirm a pseudogap in the minority channel for 62 ordered (CoFe)_(75)Ge_(25) which may cause the low damping parameters and high ΔRA in CoFeGe based current perpendicular to the plane giant magnetoresistance spin valves.