Laser-induced antiferromagnetic-like resonance in amorphous ferrimagnets

The magnetization dynamics for ferrimagnets at the angular momentum compensation temperature T_A is believed to be analogous to that for antiferromagnets. We investigated the pulsed-laser-induced magnetization dynamics in amorphous rare-earth transition-metal ferrimagnet films with a T_A just above room temperature. For a low pulse fluence, the magnetization precession frequency decreases as the applied magnetic field increases, whereas for a higher pulse fluence, it increases as the applied field increases. The result was well explained by the left-handed and right-handed precession modes of the antiferromagnetic-like resonance at temperatures below and above T_A, respectively, and the data were in agreement with the theoretical simulation. The study demonstrated the experimental route to achieving antiferromagnetic resonance in ferrimagnets using a pulsed laser.