Abstract
The ultimate control of magnetic states of matter at femtosecond (or even faster) timescales defines one of the most pursued paradigm shifts for future information technology. In this context, ultrafast laser pulses developed into extremely valuable stimuli for the all-optical magnetization reversal in ferrimagnetic and ferromagnetic alloys and multilayers, while this remains elusive in elementary ferromagnets. Here we demonstrate that a single laser pulse with sub-picosecond duration can lead to the reversal of the magnetization of bulk nickel, in tandem with the expected demagnetization. As revealed by realistic time-dependent electronic structure simulations, the central mechanism involves ultrafast light-induced torques that act on the magnetization. They are only effective if the laser pulse is circularly polarized on a plane that contains the initial orientation of the magnetization. We map the laser pulse parameter space enabling the magnetization switching and unveil rich intra-atomic orbital-dependent magnetization dynamics featuring transient inter-orbital non-collinear states. Our findings open further perspectives for the efficient implementation of optically-based spintronic devices.
Highlights
The ultimate control of magnetic states of matter at femtosecond timescales defines one of the most pursued paradigm shifts for future information technology
In conclusion, we predict via time-dependent electronic structure simulations that the so-far elusive magnetization switching in an elementary ferromagnet such as bulk fcc Ni is possible with a single laser pulse
We mapped the laser-pulse parameter regime enabling the reversal of the magnetization and found that a minimum pulse width of 60 fs is required while increasing the pulse width widens the laser fluence range allowing all-optical manipulation of the direction of the magnetization
Summary
The ultimate control of magnetic states of matter at femtosecond (or even faster) timescales defines one of the most pursued paradigm shifts for future information technology. As revealed by realistic time-dependent electronic structure simulations, the central mechanism involves ultrafast light-induced torques that act on the magnetization. They are only effective if the laser pulse is circularly polarized on a plane that contains the initial orientation of the magnetization. We address all-optical magnetization reversal and the possibility of inducing it with a single laser pulse in an elementary ferromagnet such as face fcc bulk Ni. We employ a recently developed time-dependent tight-binding framework parameterized from density functional theory (DFT) calculations, with a specific algorithm enabling us to monitor the non-linear magnetization dynamics up to a few picoseconds. We found strong non-collinear, ferromagnetic and antiferromagnetic intra-atomic transient states that are shaped by the interplay of optical inter-orbital electronic transitions and spin–orbit induced spin–flip processes
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