Phys. Rev. B
T. J. Huisman, R. V. Mikhaylovskiy, A. Tsukamoto, Th. Rasing, and A. V. Kimel
Simultaneous detection of THz emission and transient magneto-optical response is employed to study ultrafast laser-induced magnetization dynamics in three different types of amorphous metallic alloys: Co, GdFeCo and NdFeCo. A satisfactory agreement between the dynamics revealed with the help of these two techniques is obtained for Co and GdFeCo. For NdFeCo the THz emission indicates faster dynamics than the magneto-optical response. This observation indicates that in addition to spin dynamics of Fe, ultrafast laser excitation of NdFeCo triggers faster magnetization dynamics of Nd originating from its orbital momentum.