Time-Resolved Kerr Effect in Very Thin Films of CoCrPt Alloys

Fast precessional dynamics of magnetization are reported in very thin films of CoCrPt alloy with large perpendicular magnetic anisotropy. The films are fabricated with different substrate temperatures, and magnetization dynamics are investigated using time-resolved magneto-optical Kerr effect. The Kittel's equation well describes a dependency of magnetization precession frequency on an applied magnetic field direction for all the films, only when the field is relatively large. An inverse lifetime of magnetization precession, a counterpart of a line width in ferromagnetic resonance (FMR), depends strongly on the field direction even at the applied field of around 10 kOe. The Gilbert damping constant α is estimated to be ~0.05 for all the films using a model taking account of an influence of perpendicular magnetic anisotropy dispersion.