Effect of substrate roughness on the magnetic properties of CoFeB films

In this paper, a serious of CoFeB films of 30 nm prepared by a DC magnetron sputtering on Si substrates with different roughness etched by NaOH solution are investigated. It is found that the coercivity (Hc) and effective damping coefficient α are influenced by the substrate roughness of the films. As the substrate roughness increased to 73.9 nm, the Hc ranged from 14.4 Oe to 81.4 Oe; the α, from 0.012 to 0.11 at the same time. It is attributed to the function of magnetic moment pinning and magnon-magnon scattering caused by the rough substrate. Thus, the tunable performances of soft magnetism and high frequency of CoFeB films make them become potential candidates for microwave-based devices and other tunable microwave devices.