LAUSR

Abstract A series of CoFeB/Ta bilayer nano-thin films was fabricated on Si substrate using magnetron sputtering at room temperature. The temperature-and thickness-dependent dynamic magnetic properties of these films were investigated in detail using commercialized coplanar waveguide ferromagnetic resonance technique. The results showed that the Gilbert damping constant of bilayer films was monotonically decreases with the increase of temperature and thickness within certain range. We considered that the reasons for enhanced damping for the thinner magnetic films were derived from spin-pumping effect, two-magnon scatter, and magnetic dead layer. From thickness-dependent data, the surface/interface anisotropy constant, bulk damping contribution, and surface/interface damping contribution were obtained. Our results indicated that the bilayer films had perpendicular anisotropy when the CoFeB thickness was less than 1.38 nm. The results suggested that the influence of Ta on the dynamic properties of magnetic films cannot be ignored. The simplest stack structure of films was beneficial to understand the physical mechanism clearly.