Berlin 2018 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 32: Micromagnetism and computational magnetics
MA 32.2: Vortrag
Mittwoch, 14. März 2018, 15:15–15:30, H 0112
The role of longitudinal spin dynamics during magnetisation switching in FePt thin films — •Matthew Ellis, Mario Galante, and Stefano Sanvito — School of Physics and CRANN, Trinity College, Dublin 2, Ireland
L10 ordered FePt is a magnetic material of great interest for magnetic recording applications due to its large uniaxial anisotropy. Previous ab-initio studies observed that the magnetic moments localised on the Pt atoms arise due to the local exchange field provided by the neighbouring Fe atoms. As such an effective spin Hamiltonian can be derived without the Pt degrees of freedom. However, the applicability of this model in out-of-equilibrium cases where the longitudinal dynamics are important is not clear.
Here, we employ an atomistic spin model that incorporates the longitudinal fluctuations of the spin magnetic moment following the Landau Hamiltonian given by Ma and Dudarev [1]. Using this, we construct a model for L10 FePt, where the Pt magnetic moment depends linearly on its local exchange field. At temperatures close to the Curie point, we observe that despite a low net magnetisation the local ordering of Fe atoms preserves to magnetic moment of the Pt atoms. Finally, we apply this model to switching in FePt thin films using atom-resolved ab-initio computed spin-transfer torque. Whilst the torque on the Fe atoms is dominant and promotes switching the Pt torque opposes this but the exchange interaction sustains the collinearity in the film.
[1] P.-W. Ma and S. L. Dudarev, Phys. Rev. B 86, 54416 (2012).