arXiv subjects

Samuel D. Slöetjes

Publications and source records attributed to Samuel D. Slöetjes.

6 recordsLinked to original sources

arXiv2024

Modelling nanomagnet vertex dynamics through Coulomb charges

We investigate the magnetization dynamics in nanomagnet vertices often found in artificial spin ices. Our analysis involves creating a simplified model that depicts edge magnetization using magnetic charges. We utilize the model to explore the energy landscape, its associated curvatures, and the fundamental modes. Our study uncovers specific magnonic regimes and transitions between magnetization states, marked by zero-modes, which can be understood within the framework of Landau theory. To verify our model, we compare it with micromagnetic simulations, demonstrating a noteworthy agreement.

cond-mat.mes-hall↗

arXiv2023

Polymerization in magnetic metamaterials

We numerically study a mesoscopic system consisting of magnetic nanorings in the presence of thermal magnetization fluctuations. We find the formation of dipolar-field-mediated ``bonds" promoting the formation of annuli clusters, where the amount of bonds between two rings varies between zero and two. This system resembles the formation of polymers from artificial atoms, which in our case are the annuli and where the valency of the atom is set by the ring multipolarity. We investigate the thermodynamic properties of the resulting structures, and find a transition associated with the formation of the bonds. In addition, we find that the system has a tendency to form topological structures, with a distinct critical temperature in relation to the one for bond formation.

cond-mat.mes-hall↗

arXiv2022

Texture fluctuations and emergent dynamics in coupled nanomagnets

We analyse the thermal fluctuations of magnetization textures in two stray field coupled elements, forming mesospins. To this end, the energy landscape associated with the thermal dynamics of the textures is mapped out and asymmetric energy barriers are identified. These barriers are modified by changing the gap that separates the mesospins. Moreover, the coupling between the edges leads to an anisotropy in the curvature of the energy surface at the metastable minima. This yields a dynamic mode splitting of the edge modes and affects the attempt switching frequencies. Thus, we elucidate the mechanism with which the magnons in the thermal bath generate the stochastic fluctuations of the magnetization at the edges.

cond-mat.mes-hall↗

arXiv2022

Thermal excitations within and among mesospins in artificial spin ice

We provide experimental and numerical evidence for thermal excitations within and among magnetic mesospins, forming artificial spin ice structures. At low temperatures, a decrease in magnetization and increase in susceptibility is observed with increasing temperature, interpreted as an onset of thermal fluctuations of the magnetic texture within the mesospins. At elevated temperatures a pronounced susceptibility peak is observed, related to thermally induced flipping of the mesospins and a collapse of the remanent state. The fluctuations, while occurring at distinct length- and energy-scales, are shown to be tunable by the interaction strength of the mesospins.

cond-mat.mes-hall↗

arXiv2021

Temperature induced collapse of spin dimensionality in magnetic metamaterials

Spin and spatial dimensionalities are universal concepts, essential for describing both phase transitions and dynamics in magnetic materials. Lately, these ideas have been adopted to describe magnetic properties of metamaterials, as well as to replicate and explore ensembles of mesospins belonging to different universality classes. Here, we take the next step by investigating magnetic metamaterials not conforming to the conventional framework of continuous phase transitions. Instead of a continuous decrease in the moment with temperature, discrete steps are possible, resulting in a binary transition in the interactions of the elements. The transition is enabled by nucleation and annihilation of vortex cores, shifting topological charges between the interior and the edges of the elements. Consequently, the mesospins can be viewed as shifting their spin dimensionality, from 2 (XY-like) to 0, (vortices) at the transition. The results provide insight into how dynamics at different length-scales couple, which can lead to thermally driven topological transitions in magnetic metamaterials.

cond-mat.mes-hall↗

arXiv2021

The effect of confinement on thermally induced fluctuations in nanomagnets

We study the magnetization dynamics in nanomagnets excited by stochastic magnetic fields to mimic temperature in a micromagnetic framework. The effect of confinement arising from the finite size of the structures is investigated, and we visualise the spatial extension of the internal magnon modes. Furthermore, we determine the temperature dependence of the magnon modes, and focus specifically on the low frequency edge modes, which are found to display fluctuations associated with switching between C- and S-states, thus posing an energy barrier. We classify this fluctuating behaviour in three different regimes, and calculate the associated energy barriers using the Arrhenius law.

cond-mat.mes-hall↗