Magnetization relaxation and structure of CoFeGe alloys

The magnetic relaxation of 10 and 50 nm thin films of (CoFe)100−xGex (0 at. %≤x≤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 B2 ordered (CoFe)75Ge25 which may cause the low damping parameters and high ΔRA in CoFeGe based current perpendicular to the plane giant magnetoresistance spin valves.