D. Wang, A. J. Schellekens, B. Koopmans
Laser induced ultrafast demagnetization in ferromagnetic metals was discovered almost 20 years ago, but currently there is still lack of consensus on the microscopic mechanism responsible for the corresponding transfer of angular momentum and energy between electron, lattice and spin subsystems. A distinct, but intrinsically correlated phenomenon occurring on a longer timescale is the magnetization oscillation after the ultrafast demagnetization process, if a magnetic field is applied to tilt the magnetization vector away from its easy direction. Based on a microscopic three temperature model, which adapts the Elliott-Yafet scattering between electrons and phonons to explain the ultrafast demagnetization process, a unified theoretical description of both phenomena is proposed. In our unified description, the ultrafast demagnetization is mediated by the Elliott-Yafet scattering, while the resultant change of anisotropy is responsible for the following magnetization oscillation. Theoretical prediction with plausible parameters are in excellent agreement with experimental data measured using time resolved magneto-optical Kerr effect in an in-plane magnetized Pt/Co/Pt thin film with perpendicular interface anisotropy. This agreement between theory and experiment provides more insight into the microscopic mechanism behind the ultrafast demagnetization process. Furthermore, the model proposed here could also be used to study the magnetization dynamics triggered by the modification of anisotropy field through ultrafast laser heating.
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http://arxiv.org/abs/1308.0976
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