Self-assembly of Dipolar Crystals from Magnetic Colloids

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Hauptverfasser: Singh, Anuj Kumar, Puri, Sanjay, Banerjee, Varsha
Format: Preprint
Veröffentlicht: 2025
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author Singh, Anuj Kumar
Puri, Sanjay
Banerjee, Varsha
author_facet Singh, Anuj Kumar
Puri, Sanjay
Banerjee, Varsha
contents We study the self-assembly of magnetic colloids using the Stockmayer (SM) model characterized by short-range Lennard-Jones interactions and long-range dipole-dipole interactions. Using molecular dynamics simulations, we design cooling protocols that yield perfectly assembled single-domain magnetic crystals. We identify cooling rates at which the system transforms from an amorphous glass to a crystal, where magnetic ordering promotes crystalline order. Remarkably, we observe that the latter develops via a spontaneous transition rather than through the traditional nucleation and growth mechanism. For a weakly dipolar fluid ($μ=1$), this self-assembly results in a face-centered cubic (FCC) colloidal crystal with dipole moments chained along the (111) direction. For fluids with higher dipole moment ($μ= 2.5$), the crystal structure shifts towards a body-centered orthorhombic (BCO) arrangement due to the compression of chains from strong dipolar attractions. These results provide valuable insights into the mechanisms driving crystallization in magnetic fluids, opening new avenues for understanding the formation of magnetically responsive colloidal magnetic crystals with promising applications.
format Preprint
id arxiv_https___arxiv_org_abs_2502_15265
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Self-assembly of Dipolar Crystals from Magnetic Colloids
Singh, Anuj Kumar
Puri, Sanjay
Banerjee, Varsha
Soft Condensed Matter
We study the self-assembly of magnetic colloids using the Stockmayer (SM) model characterized by short-range Lennard-Jones interactions and long-range dipole-dipole interactions. Using molecular dynamics simulations, we design cooling protocols that yield perfectly assembled single-domain magnetic crystals. We identify cooling rates at which the system transforms from an amorphous glass to a crystal, where magnetic ordering promotes crystalline order. Remarkably, we observe that the latter develops via a spontaneous transition rather than through the traditional nucleation and growth mechanism. For a weakly dipolar fluid ($μ=1$), this self-assembly results in a face-centered cubic (FCC) colloidal crystal with dipole moments chained along the (111) direction. For fluids with higher dipole moment ($μ= 2.5$), the crystal structure shifts towards a body-centered orthorhombic (BCO) arrangement due to the compression of chains from strong dipolar attractions. These results provide valuable insights into the mechanisms driving crystallization in magnetic fluids, opening new avenues for understanding the formation of magnetically responsive colloidal magnetic crystals with promising applications.
title Self-assembly of Dipolar Crystals from Magnetic Colloids
topic Soft Condensed Matter
url https://arxiv.org/abs/2502.15265