  The ability to tailor the damping factor is essential for spintronic and
spin-torque applications. Here, we report an approach to manipulate the damping
factor of FeGa/MgO(001) films by oblique deposition. Owing to the defects at
the surface or interface in thin films, two-magnon scattering (TMS) acts as a
non-Gilbert damping mechanism in magnetization relaxation. In this work, the
contribution of TMS was characterized by in-plane angular dependent
ferromagnetic resonance (FMR). It is demonstrated that the intrinsic Gilbert
damping is isotropic and invariant, while the extrinsic mechanism related to
TMS is anisotropic and can be tuned by oblique deposition. Furthermore, the two
and fourfold TMS related to the uniaxial magnetic anisotropy (UMA) and
magnetocrystalline anisotropy were discussed. Our results open an avenue to
manipulate magnetization relaxation in spintronic devices.
