Abstract
Spintronics had a widespread impact over the past decades due to transferring information by spin rather than electric currents. Its further development requires miniaturization and reduction of characteristic timescales of spin dynamics combining the sub-nanometre spatial and femtosecond temporal ranges. These demands shift the focus of interest towards the fundamental open question of the interaction of femtosecond spin current (SC) pulses with a ferromagnet (FM). The spatio-temporal properties of the impulsive spin transfer torque exerted by ultrashort SC pulses on the FM open the time domain for probing non-uniform magnetization dynamics. Here we employ laser-generated ultrashort SC pulses for driving ultrafast spin dynamics in FM and analysing its transient local source. Transverse spins injected into FM excite inhomogeneous high-frequency spin dynamics up to 0.6 THz, indicating that the perturbation of the FM magnetization is confined to 2 nm.
Highlights
Spintronics had a widespread impact over the past decades due to transferring information by spin rather than electric currents
Aiming at understanding characteristic microscopic spin transfer torque (STT) length and timescales, we address this challenge by studying spin dynamics in considerably thicker FM layers, so that both interface and bulk STT contributions[22,23] might be active
The latter can mediate an inhomogeneous perturbation of magnetization and promote excitation of spin waves in a FM film, which extends spin dynamics into higherfrequency range
Summary
Spintronics had a widespread impact over the past decades due to transferring information by spin rather than electric currents. Its further development requires miniaturization and reduction of characteristic timescales of spin dynamics combining the sub-nanometre spatial and femtosecond temporal ranges These demands shift the focus of interest towards the fundamental open question of the interaction of femtosecond spin current (SC) pulses with a ferromagnet (FM). Aiming at understanding characteristic microscopic STT length and timescales, we address this challenge by studying spin dynamics in considerably thicker FM layers, so that both interface and bulk STT contributions[22,23] might be active The analysis of their importance and the relevant length scales is the major aim of our work. We argue below that in our experiment, the bulk STT is damped in the vicinity of the Fe/Au interface emphasizing the importance of the interface STT contribution The latter can mediate an inhomogeneous perturbation of magnetization and promote excitation of spin waves in a FM film, which extends spin dynamics into higherfrequency range. MOKE that the ultrashort laser-induced SC pulses constitute a convenient tool to excite spin waves and study the interaction of spins with a non-collinear magnetization
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