Ultrafast Path for Optical Magnetization Reversal via a Strongly Nonequilibrium State

Using time-resolved single-shot pump-probe microscopy we unveil the mechanism and the time scale of all-optical magnetization reversal by a single circularly polarized 100 fs laser pulse. We demonstrate that the reversal has a linear character, i.e., does not involve precession but occurs via a strongly nonequilibrium state. Calculations show that the reversal time which can be achieved via this mechanism is within 10 ps for a 30 nm domain. Using two single subpicosecond laser pulses we demonstrate that for a $5\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ domain the magnetic information can be recorded and readout within 30 ps, which is the fastest ``write-read'' event demonstrated for magnetic recording so far.