Berlin 2012 – scientific programme

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MA: Fachverband Magnetismus

MA 15: Magnetization / Demagnetization Dynamics I

MA 15.5: Talk

Tuesday, March 27, 2012, 10:45–11:00, H 1012

Ultrafast element specific demagnetisation dynamics of Fe and Ni in FeNi Alloys — •Denise Hinzke¹, Unai Atxitia², Oksana Chubykalo-Fesenko², Karel Carva³, Peter Openeer³, and Ulrich Nowak¹ — ¹Universität Konstanz, 78457 Konstanz, Germany — ²Instituto de Ciencia de Materiales de Madrid, 28049 Madrid, Spain — ³Uppsala University, 75120 Uppsala, Sweden

Since the first observation of the quenching of magnetisation in Ni on the sub-ps timescales [1], ultrafast demagnetisation was intensively studied, both experimentally and theoretically. Recently, element-specific techniques were used to observe the element-resolved dynamics after optical excitation on fs timescales [2,3]. In order to get an deeper insight of the underlying mechanism we perform atomistic spin model simulations of fcc Permalloy.

We model FeNi using a classical spin Hamiltonian with exchange integrals constructed on the basis of spin density functional theory. Langevin dynamics simulation, i. e. simulations of the stochastic Landau-Lifshitz-Gilbert equation of motion are performed. The differences of the dynamics of Fe and Ni sublattices on the fs timescale is investigated for different model assumptions such as temperature and damping and compared with the dynamics gained in the framework of a two sublattices Landau-Lifshitz-Bloch equation of motion.

[1] E. Beaurepaire et al., Phys. Rev. Lett. 76, 4250 (1996). [2] C. La-O-Vorakiat et al., Phys. Rev. Lett. 103, 257402 (2009). [3] I. Radu et al., Nature 472, 205 (2011). Funding from EC collaborative project FP 7 (FemtoSpin) and the CAP Konstanz is acknowledged.