In recent years, there has been an intense interest in understanding themicroscopic mechanism of thermally induced magnetization switching driven by afemtosecond laser pulse. Most of the effort has been dedicated to periodiccrystalline structures while the amorphous counterparts have been less studied.By using a multiscale approach, i.e. first-principles density functional theorycombined with atomistic spin dynamics, we report here on the very intricatestructural and magnetic nature of amorphous Gd-Fe alloys for a wide range of Gdand Fe atomic concentrations at the nanoscale level. Both structural anddynamical properties of Gd-Fe alloys reported in this work are in goodagreement with previous experiments. We calculated the dynamic behavior ofhomogeneous and inhomogeneous amorphous Gd-Fe alloys and their response underthe influence of a femtosecond laser pulse. In the homogeneous sample, the Fesublattice switches its magnetization before the Gd one. However, the temporalsequence of the switching of the two sublattices is reversed in theinhomogeneous sample. We propose a possible explanation based on a mechanismdriven by a combination of the Dzyaloshiskii-Moriya interaction and exchangefrustration, modeled by an antiferromagnetic second-neighbour exchangeinteraction between Gd atoms in the Gd-rich region. We also report on theinfluence of laser fluence and damping effects in the all-thermal switching.
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