Role of antisite disorder on intrinsic Gilbert damping in L 10 FePt films

The impact of antisite disorder x on the intrinsic Gilbert damping α₀ in well-ordered L 1₀ FePt films is investigated by time-resolved magneto-optical Kerr effect. The variation of x mainly affects the electron scattering rate 1 /τ_e , while other leading parameters remain unchanged. The experimentally observed linear dependence of α₀ on 1 /τ_e indicates that spin relaxation is through electron interband transitions, as predicted by the spin-orbit coupling torque correlation model. Measurements at low temperature show that α₀ remains unchanged with temperature even for FePt with very high chemical order, indicating that electron-phonon scattering is negligible. Moreover, as x decreases, the perpendicular magnetic anisotropy increases, and the Landau g factor exhibits a negative shift due to an increase in orbital momentum anisotropy. Our results will facilitate the design and exploration of magnetic alloys with large magnetic anisotropy and desirable damping properties.