Process of Magnetization Reversal in a Spot Heated by Pulsed Laser Beam

The process of magnetization reversal in a bit written by a light beam was observed using a micro-Kerr effect measurement technique. Pulsed laser light (of wave-length 830 nm), combined with a synchronized, sinusoidally oscillating bias magnetic field, caused repeated writing and erasing of a bit. By monitoring cw laser light (633 nm) focused on the bit, the change in the Rerr rotation angle due to the rise in temperature was measured. Samples used were amorphous rare-earth--transition-metal (RE-TM) thin films (TbFeCo) sputtered onto glass substrates. For TM-rich films, domains in spots irradiated by laser light in a zero bias magnetic field tend to include magnetic reversal regions; for RE-rich films, in contrast, there is a single stable domain.