Finite dipolar hexagonal columns on piled layers of triangular lattice

TL;DR

This study uses Monte Carlo simulations to explore finite size effects in dipolar hexagonal columns of magnetic nanoparticles, revealing vortex states and layer-dependent ground states influenced by system size and structure.

Contribution

It provides new insights into how finite size and layer configuration affect magnetic ground states in dipolar nanoparticle arrays.

Findings

Observation of vortex states in close-packed structures

Layer-dependent ground states in compressed systems

Finite size effects induce orientation transitions

Abstract

We have investigated, by the Monte Carlo simulation, spin systems which represent moments of arrayed magnetic nanoparticles interacting with each other only by the dipole-dipole interaction. In the present paper we aim the understanding of finite size effects on the magnetic nanoparticles arrayed in hexagonal columns cut out from the close-packing structures or from those with uniaxial compression. In columns with the genuine close-packing structures, we observe a single vortex state which is also observed previously in finite 2-dimensional systems. On the other hand in the system with the inter-layer distance set $1/\sqrt{2}$ times of the close-packing one, we found ground states which depend on the number of layers. The dependence is induced by a finite size effect and is related to a orientation transition in the corresponding bulk system.