High frequency dynamics and magnetic anisotropy of bcc Co films grown on Si (001) substrate

Dynamic magnetization and magnetic anisotropy of Cu/bcc-Co/CoSi2/Si(001) system were investigated by Magneto-Optical Kerr Effect (MOKE) analysis and vector network analyzer ferromagnetic resonance (VNA-FMR). Typical fourfold magnetocrystalline anisotropy of bcc Co film and superposed uniaxial magnetic anisotropy were observed. The uniaxial magnetic anisotropy originated from shape anisotropy as confirmed by micromagnetic simulation. The large magnetocrystalline anisotropy results in high resonance frequency even in the zero applied field. The Gilbert damping parameter alpha obtained by analysis of the dynamic process is close to the theoretically estimated value of bcc phase Co. The Gilbert damping parameter of the bcc-Co film is larger than those of fcc-Co and hcp-Co films. This work indicates the Co damping parameter can be enhanced by using bcc structure, which will help create high-speed magnetoelectronic devices.