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Condensed Matter, Mesoscale and Nanoscale Physics, cond-mat.mes-hall
Abstract:
In this Article we discuss a micromagnetic modelling approach to describe the
ultrafast spin-transfer torque excitation of coherent and incoherent magnons on
the nanoscale. Implementing the action of a femtosecond spin current pulse
entering an orthogonally magnetized thin ferromagnetic film, we reproduce
recent experimental results and reveal the factors responsible for the unequal
excitation efficiency of various spin waves. Our findings are in an excellent
agreement with the results of an analytical description of spin-wave excitation
based on classical kinetic equations. Furthermore, we suggest an experimental
design allowing for the excitation of laterally propagating spin waves beyond
the optical diffraction limit. Our findings demonstrate that the classical
micromagnetic picture retains its predictive and interpretative power on
femtosecond temporal and nanometer spatial scales.
