Ultrafast magnetization dynamics in the vicinity of spin reorientation transition in TbCo2/FeCo heterostructures

Abstract

The magnetic moment dynamics excited by 35 fs laser pulses in TbCo2/FeCo heterostructure is experimentally investigated by pump-probe technique. The studies are carried out in two typical geometries with magnetizing field perpendicular and along to easy magnetization axis. In "the easy axis" orientation, high-frequency oscillations of magnetic moment odd with respect to the sign of the magnetizing field are observed using the magneto-optical Kerr effect. In the perpendicular "hard axis" orientation corresponding to the spin reorientation phase, the experiment shows oscillations that are even with respect to the field. The maximum angle of Kerr rotation as function of magnetizing field strength depicts specfic hysteretic loop that reveals ultrafast optical control of uniaxial magnetic anisotropy originally induced during deposition of the heterostructure in DC magnetic field. The results provide new ways to ultrafast control of magnetic states in exchange coupled intermetallic heterostructures designed for spintronic applications.