Modeling magnetization oscillations in ferromagnetic cobalt disks exposed to picosecond laser pulses

Magnetic reversal of a ferromagnetic single-domain nanoparticle in the form of a disk contained in a multilayer nanostructure irradiated by linearly and circularly polarized picosecond laser pulses is modeled. It is shown that heating of the disk by the laser light causes a change in its direction of magnetization. This is accompanied by oscillations in the magnetization that decay over 1–16 ns. The frequencies of these oscillations lie in the range of 0.5–26 GHz. The main reason for the magnetic reversal of the disk is a change in the magnetic anisotropy energy during heating. The laser pulses also create a spin-polarized current and an inverse Faraday magneto-optical field in the structure, which influence the duration, amplitude, and frequency of the magnetization oscillations.