Description of impact
Central quest in this research theme is to understand and control
magnetization dynamics in its ultimate limits. Most extreme case is met when
exciting magnetic matter by femtosecond laser pulses, driving a system into a
strongly non-equilibrium state. Understanding this regime has been a
significant challenge, but rapid progress is being witnessed. Most excitingly,
it has been found that the laser excitation triggers a wide range of phenomena,
ranging from spin wave excitation and magnetic phase transitions, to the very
recently discovered all-optical switching and laser-induced spin-transfer
torque. Our group is active in studying the fundamentals mechanisms leading to
those novel phenomena, but also explores their potential use in entirely novel
device concepts for ultrafast magnetic storage, memory and logic. Furthermore,
bridging the regime between high-frequency electronics and femtosecond laser
excitations provides exciting opportunities.
Understanding non-equilibrium femtosecond magnetization dynamics
Femtosecond laser-excitation drives a ferromagnet into a state where
electronic, spin and lattice degrees of freedom are no longer in mutual
equilibrium. Combining time-resolved MOKE experiments on especially engineered
multilayered structures, as well as theoretical modelling help us to understand
the mechanism governing the various sub-picosecond spin-related processes
Femtosecond laser-induced spin transfer & all-optical switching
We pioneered the use of femtosecond laser pulses to trigger spin current
at the ultrafast time scales. Apart from affecting the rate at which magnetic
order is locally lost, it was also shown that a laser-induced spin transfer
torque can be generated between adjacent layers. Another novel approach is to
exploit non-equilibrium exchange rather than spin currents to control the
magnetic state.
Precessional dynamics and damping phenomena
Precessional dynamics and Gilbert damping in nanomagnetic structures and
devices proceed typically at GHz frequencies, a regime where high-frequency
electronics and pulsed laser studies can complement. Explorations in this
regime are of extreme relevance for novel routes in spintronics, ranging from
switching nanomagnets to domain wall phenomena – all actively being explored
within our group.
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