Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 30: Skyrmions 3 (joint session MA/KFM)

KFM 30.6: Vortrag

Freitag, 9. September 2022, 10:45–11:00, H37

Thermal properties of magnetic skyrmions — •Balázs Nagyfalusi1, László Udvardi2,3, and László Szunyogh2,31Wigner Research Center for Physics, Institute for Solid State Physics and Optics, Budapest, Hungary — 2Budapest University of Technology and Economics, Budapest Hungary — 3MTA-BME Condensed Matter Research Group, Budapest, Hungary

We have recently implemented metadynamics in Monte Carlo simulation code1, which has been modified to use the topological charge Q of magnetic skyrmions as collective variable. The free energy can thus be determined as a function of Q and its equilibrium value can be explored as a function of temperature. The knowledge of the free energy F(Q;T) also permits to evaluate the chemical potential µ of the skyrmions.

We investigated the thermal evolution of magnetic skyrmions in a Pt95Ir5/Fe bilayer on Pd(111) and an FePd bilayer on Ir(111) substrate in the presence of a normal-to-plane external magnetic field. The equilibrium number of skyrmions and the phase boundaries are in good agreement with previous studies2,3. For the former system we found that Q has a maximum around 60 K and below this temperature this number drops rapidly, while for the later system it freezes in as the skyrmion lattice is a ground state of the system. The slope of µ(T) also distinguishes the different ground states of the two system.

1. Nagyfalusi et al., Phys. Rev. B 100, 174429 (2019)

2. Rózsa et al., Phys. Rev. B 93, 024417 (2016)

3. Schick et al., Phys. Rev. B 103, 214417 (2021)

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