Femtosecond spin dynamics of epitaxial Cu(111)/Ni/Cu wedges

The femtosecond spin dynamics in ferromagnetic metals is studied using time -resolved magneto-optics on an epitaxial Cu(111)/Ni/Cu wedge. A novel and s ensitive double modulation scheme is introduced. The induced Kerr rotation and ellipticity are separately measured, and display a contrasting behavior during the first 500 fs after excitation. This proves the absence of a dir ect relation between the magneto-optical signal and the magnetization. A sy stematic study of the spin dynamics along the nickel wedge shows a surprisi ngly small influence of interface scattering, magnetic anisotropy, and morp hology on the dynamics. (C) 2000 American Institute of Physics. [S0021-8979 (00)64408-0].