Ultrafast optical modification of magnetic anisotropy and stimulated precession in an epitaxial Co2 MnAl thin film

An all-optical pump-probe method was used to study magnetization precession in an epitaxial Co2 MnAl Heusler alloy thin film. The frequency and amplitude of precession showed a clear fourfold variation as the orientation of the static field was applied in different directions within the plane of the film, revealing that the precession is induced by an ultrafast modification of the magnetocrystalline anisotropy field. The effective fields acting upon the magnetization have been determined and the damping parameter is found to decrease rapidly as the strength of the applied field is increased.