Magnetization relaxation and structure of CoFeGe alloys

The magnetic relaxation of 10 and 50 nm thin films of ( CoFe ) 100 − x Ge x ( 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 B 2 order for these compositions. First principles calculations confirm a pseudogap in the minority channel for B 2 ordered ( CoFe ) 75 Ge 25 which may cause the low damping parameters and high Δ R A in CoFeGe based current perpendicular to the plane giant magnetoresistance spin valves.