Regensburg 2025 – scientific programme
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MA: Fachverband Magnetismus
MA 46: Surface Magnetism
MA 46.3: Talk
Friday, March 21, 2025, 10:00–10:15, H19
Influence of higher order interactions on the thermal behaviour of magnetic order in Mn/Re(0001) — •Leo Kollwitz1, Moritz Alexander Goerzen2,1, Hendrik Schrautzer3,1, and Stefan Heinze1 — 1Institute of Theoretical Physics and Astrophysics, Kiel University, 24098 Kiel, Germany — 2CEMES, Université de Toulouse, CNRS, France — 3Science Institute and Faculty of Physical Sciences, University of Iceland, 107 Reykjavík, Iceland
Non-trivial multi-Q states, which consist of the superposition of periodically modulated spin textures, are known to arise in Mn monolayers on the Re(0001) substrate due to higher-order exchange interactions (HOI) [1]. However, to date little is known about the thermodynamic properties of these highly ordered phases.
Here, we perform Monte Carlo simulations based on an atomistic spin model parametrized by density functional theory, in order to investigate thermal phase transitions in this material. It is found that the explicit consideration of HOI in the simulations leads to a significant decrease of the Néel temperature and to an introduction of a new transition between single-Q and multi-Q states at low temperatures. Recent experiments show that a similar transition occurs in Co1/3TaS2 [2]. By modelling the free energy landscape of the system in terms of thermal excitations, which are expressed in the eigenbasis of the Hamiltonian, we further identify the important degrees of freedom responsible for this additional entropy mediated transition.
[1] J. Spethmann et al, Phys. Rev. Lett. 124, 227203 (2020)
[2] P. Park et al, Nat. Comm. 14, 8346 (2023)
Keywords: Monte Carlo; Phase transitions; Multi-Q states; Higher-order interactions; Ultrathin films