Ferromagnetic resonance of CoFeB/Ta/CoFeB spin valves versus CoFeB film

In MgO/CoFeB/MgO/Ta (single layer) and MgO/CoFeB/Ta/CoFeB/MgO/Ta spin valve (bilayer), the orientation dependences of ferromagnetic resonance (FMR) have been analyzed. Magnetic anisotropy constants as well as damping constants have been extracted. The differences between the anisotropy constants in single-layer film and spin valve MgO/CoFeB/Ta/CoFeB/MgO/Ta are explained by dipole magnetic interaction between ferromagnetic layers. The main part of the linewidth corresponds to inhomogeneous widening, while smaller part is provided by interface exchange fluctuations. The FMR lineshape can be explained by standard FMR Lorenz line and nonresonant absorption provided by inverse spin Hall effect.