  All-optical ultrafast magnetization switching in magnetic material thin film
without the assistance of an applied external magnetic field is being explored
for future ultrafast and energy-efficient magnetic storage and memories. It has
been shown that femto-second light pulses induce magnetization reversal in a
large variety of magnetic materials. However, so far, only GdFeCo-based
ferrimagnetic thin films exhibit magnetization switching via a single optical
pulse. Here we demonstrate the single-pulse switching of Co/Pt multilayers
within a magnetic spin-valve structure ([Co/Pt] / Cu / GdFeCo) and further show
that the four possible magnetic configurations of the spin valve can be
accessed using a sequence of single femto-second light pulses. Our experimental
study reveals that the magnetization final state of the ferromagnetic [Co/Pt]
layer is determined by spin-polarized hot electrons generated by the light
pulse interactions with the GdFeCo layer. This work provides a new approach to
deterministically switch ferromagnetic layers and a pathway to engineering
materials for opto-magnetic multi-bit recording.
