Characterisation of the magnetic response of nanoscale magnetic filaments in applied fields

Deniz Mostarac, Pedro A. Sánchez, Sofia Kantorovich

Publications: Contribution to journalArticlePeer Reviewed

Abstract

Incorporating magnetic nanoparticles (MNPs) within permanently crosslinked polymer-like structures opens up the possibility for synthesis of complex, highly magneto-responsive systems. Among such structures are chains of prealigned magnetic (ferro- or super-paramagnetic) monomers, permanently crosslinked by means of macromolecules, which we refer to as magnetic filaments (MFs). In this paper, using molecular dynamics simulations, we encompass filament synthesis scenarios, with a compact set of easily tuneable computational models, where we consider two distinct crosslinking approaches, for both ferromagnetic and super-paramagnetic monomers. We characterise the equilibrium structure, correlations and magnetic properties of MFs in static magnetic fields. Calculations show that MFs with ferromagnetic MNPs in crosslinking scenarios where the dipole moment orientations are decoupled from the filament backbone, have similar properties to MFs with super-paramagnetic monomers. At the same time, magnetic properties of MFs with ferromagnetic MNPs are more dependent on the crosslinking approach than they are for ones with super-paramagnetic monomers. Our results show that, in a strong applied field, MFs with super-paramagnetic MNPs have similar magnetic properties to ferromagnetic ones, while exhibiting higher susceptibility in low fields. We find that MFs with super-paramagnetic MNPs have a tendency to bend the backbone locally rather than to fully stretch along the field. We explain this behaviour by supplementing Flory theory with an explicit dipole–dipole interaction potential, with which we can take in to account folded filament configurations. It turns out that the entropy gain obtained through bending compensates an insignificant loss in dipolar energy for the filament lengths considered in the manuscript.
Original languageEnglish
Article number13933-13947
Pages (from-to)13933-13947
Number of pages15
JournalNanoscale
Volume12
Issue number26
Early online date14 May 2020
DOIs
Publication statusPublished - 14 Jul 2020

Austrian Fields of Science 2012

  • 103023 Polymer physics
  • 103017 Magnetism
  • 103029 Statistical physics

Keywords

  • ARCHITECTURES
  • ARRAYS
  • BRUSHES
  • COLLOIDAL POLYMERS
  • DIPOLAR CHAINS
  • DYNAMICS
  • FABRICATION
  • FORCES
  • NANOPARTICLE CHAINS

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