Self-organization of magnetic moments in dipolar chains with restricted degrees of freedom

Alexander F. Pshenichnikov and Andrey A. Kuznetsov
Phys. Rev. E 92, 042303 – Published 6 October 2015

Abstract

Equilibrium behavior of a single chain of dipolar spheres is investigated by the method of molecular dynamics in a wide range of the dipolar coupling constant λ. Two cases are considered: rodlike and flexible chains. In the first case, particle centers are immovably fixed on one axis, but their magnetic moments retain absolute orientational freedom. It has been found that at λ1.5 particle moments are chiefly aligned parallel to the chain axis, but the total moment of the chain continuously changes its sign with some mean frequency, which exponentially decreases with the growth of λ. Such behavior of the rodlike chain is analogous to the Néel relaxation of a superparamagnetic particle with a finite energy of magnetic anisotropy. In the flexible chain particles are able to move in the three-dimensional space, but the distance between centers of the first-nearest neighbors never exceeds a given limiting value rmax. If rmaxd (d is the particle diameter) then the most probable shape of the chain of five or more particles at λ6 is that of a ring. The behavior of chains with rmax2d is qualitatively different: At λ4 long chains collapse into dense quasispherical globules and at λ8 these globules take toroidal configuration with a spontaneous azimuthal ordering of magnetic dipoles. With the increase of rmax to larger values (rmax>10d) globules expand and break down to form separate rings.

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  • Received 6 July 2015

DOI:https://doi.org/10.1103/PhysRevE.92.042303

©2015 American Physical Society

Authors & Affiliations

Alexander F. Pshenichnikov and Andrey A. Kuznetsov

  • Laboratory of Dynamics of Dispersed Systems, Institute of Continuous Media Mechanics UB RAS, Korolyov Street 1, Perm 614013, Russia

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Issue

Vol. 92, Iss. 4 — October 2015

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