Drag effect induced large anisotropic damping behavior in magnetic thin films with strong magnetic anisotropy.

The determination of intrinsic Gilbert damping is one of the central interests in the field of spintronics. However, some external factors in magnetic films tend to play a remarkable role in the magnetization dynamics. Here, we present a comprehensive study of the magnetic relaxation in ferromagnetic films with various in-plane magnetic anisotropy via ferromagnetic resonance technique. We find that the magnetic drag effect can result in the resonant linewidth broadening and the nonlinear dependence of linewidth on frequency stemming from field-magnetization misalignment. As a result, this could lead to the imprecise extraction of the key dynamic parameter-Gilbert damping and cause the confusing behaviors of ultra-low and anisotropic damping in thin films and multi-layers with high magnetic anisotropy. Our results provide a crucial way for the accurately quantitative estimation of the Gilbert damping in spintronics measurements.