Tuning of the intrinsic magnetic damping parameter in epitaxial CoNi(001) films : Role of the band-filling effect

The band-filling effect, which is due to tuning the electron occupation number near the Fermi level, on the intrinsic magnetic damping parameter is demonstrated by employing high-quality epitaxial Co_1-xNiₓ alloy films, in which the Fermi level and the density of states can be continuously tuned by varying the Ni concentration x. The intrinsic magnetic damping parameter, measured by the time-resolved magneto-optical Kerr effect, changes weakly at small x and increases sharply for $x>0.80$. The experimental results are well reproduced by the density functional theory calculation. More interestingly, the magnetic damping parameter and the density of states near the Fermi level share similar variation trends, demonstrating their correlation. The band-filling effect in $3d$ magnetic transition metal alloys provides a way to tune the magnetic damping parameter as a key element in the controlg of energy loss and speed of spintronic devices.