A Two‐Parameter Model for Colloidal Particles with an Extended Magnetic Cap. Issue 19 (1st October 2019)

• Record Type: Journal Article
• Authors: Neumann, Maximilian; Strobel, Aaron; Al-Saadawi, Yara; Steinbach, Gabi; Erbe, Artur; Gemming, Sibylle
• Other Names: Zahn Dietrich R.T. guestEditor.; Schulz Stefan E. guestEditor.; Hiller Karla guestEditor.; Wagner Christian guestEditor.; Reuter Danny guestEditor.; Otto Thomas guestEditor.
• Is Part Of: Physica status solidi. Volume 216:Issue 19(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-10-01
• Subjects: capped colloids -- magnetic colloids -- self-assemblies -- simulations -- theories; Solid state physics -- Periodicals; Solids -- Industrial applications -- Periodicals; 530.41
• DOI: 10.1002/pssa.201900506
• Languages: English
• ISSNs: 1862-6300

Abstract

Abstract : Self‐assembly of magnetic colloidal particles in solution has successfully been simulated by hard‐ or soft‐sphere models with a set of embedded magnetic point dipoles, and the position and orientation of each dipole are adapted to mimic the magnetization distribution. Herein, a conceptually simpler approach is introduced for magnetically capped colloidal particles, which replaces the set of dipoles by the extended magnetization distribution of a single conductive loop. Only two parameters are required to characterize the magnetization distribution: the diameter of the loop and its radial off‐center shift within the sphere. This approach reflects the radial symmetry and the spatial extension of the magnetic cap. At larger distance and in the limit of very small loops that model reproduces the far field and particle arrangements obtained with the single, radially shifted dipole model. For larger loop radii, additional stable assembly patterns are obtained, which occur in experiments, but cannot be simulated with a single shifted dipole model. Abstract : Simulated and experimental dimers of magnetically capped particles as a function of cap thickness and extension are introduced. The magnetization is modeled by the stray field of a conductive loop within a hard sphere. Ferromagnetic dimer coupling is obtained for small, thin cap models, antiparallel for thick, extended caps. The experimental configuration is antiparallel with an intermediate cap‐axis angle.