Projects per year
Abstract
Precise modeling of the magnetization dynamics of nanoparticles with finitesize effects at fast varying temperatures is a computationally challenging task. Based on the LandauLifshitzBloch (LLB) equation we derive a coarsegrained model for disordered ferrimagnets, which is both fast and accurate. First, we incorporate stochastic fluctuations to the existing ferrimagnetic LLB equation. Further, we derive a thermodynamic expression for the temperaturedependent susceptibilities, which is essential to model finitesize effects. Together with the zerofield equilibrium magnetization the susceptibilities are used in the stochastic ferrimagnetic LLB to simulate a ferrimagnetic Gd30 (FeCo)(70) particle with a diameter of 5 nm and a height of 10 nm under various external applied fields and heat pulses. The obtained trajectories agree well with those of an atomistic model, which solves the stochastic LandauLifshitzGilbert equation for each atom. Finally, we apply a 50fs heat pulse with a maximum temperature of 1193 K to a Gd24 (FeCo)(76) particle of the same size to test the proposed model for alloptical switching (AOS). We observe switching with a ferromagneticlike state, which was identified to be the key for AOS in GdFeCo. Although the coarsegrained model in general shows remarkably good agreement with atomistic simulations, the computed switching probability is lower than expected. The magnetization trajectories seem to be too far away from equilibrium for ultrashort and very high heat pulses, which are typical for AOS. This leads to the conclusion that either the model needs higherorder corrections to accurately describe AOS, or that the twospin model is not capable of describing deterministic AOS at all.
Original language  English 

Article number  054401 
Number of pages  11 
Journal  Physical Review B 
Volume  100 
Issue number  5 
DOIs  
Publication status  Published  1 Aug 2019 
Austrian Fields of Science 2012
 103018 Materials physics
Projects
 2 Finished

Beating the recording quadrilemma using Curie temperature modulated structures
Süss, D. & Vranckx Herrera, S. E.
1/01/16 → 31/12/18
Project: Research funding

Thermally Controlled Magnetization Dynamics
Süss, D., Vranckx Herrera, S. E. & Praetorius, D.
1/01/15 → 30/09/18
Project: Research funding