Structure organization and magnetic properties of microscale ferrogels: The effect of particle magnetic anisotropy

Abstract

The equilibrium structure and magnetic properties of a ferrogel object of small size (microferrogel(MFG)) are investigated by coarse-grained molecular dynamics. As a generic model of a microferrogel (MFG), a sample with a lattice-like mesh is taken. The solid phase of the MFG consists of magnetic (e.g., ferrite) nanoparticles which are mechanically linked to the mesh making some part of its nodes. Unlike previous models, the finite uniaxial magnetic anisotropy of the particles, as it is the case for real ferrogels, is taken into account. For comparison, two types of MFGs are considered: MFG-1, which dwells in virtually non-aggregated state independently of the presence of an external magnetic field, and MFG-2, which displays aggregation yet under zero field. The structure states of the samples are analyzed with the aid of angle-resolved radial distribution functions and cluster counts. The results reveal the crucial role of the matrix elasticity on the structure organization as well as on magnetization of both MFGs. The particle anisotropy, which plays insignificant role in MFG-1 (moderate interparticle magnetodipole interaction), becomes an important factor in MFG-2 (strong interaction). There, the restrictions imposed on the particle angular freedom by the elastic matrix result in notable diminution of the particle chain lengths as well as the magnetization of the sample. The approach proposed enables one to investigate a large variety of MFGs, including those of capsule type and to purposefully choose the combination of their magnetoelastic parameters.

Soft magnetic nanocomposites based on adaptive matrix of wormlike surfactant micelles

“…A wide range of linear rheological response and a strongly improved sedimentation stability can be obtained by using magnetic elastomers/gels. 3,[19][20][21][22] But in these materials, chemical network limits considerably the mobility of particles and as a consequence the magnetic response. To get a signicant magnetic response in this case it is necessary to use a high amount of particles (above 10 vol%) and elds above 0.1 T.…”

The effect of magnetic nanoparticle concentration on the structure organisation of a microferrogel

“…For that, we use an indicator function q(j,d ) introduced in Ref. [7]. It renders the fraction of NPs possessing at least j neighbours whose center-to-center distances are less or equal the valued that is chosen quite close to d np ; in our calculations we setd = 1.1d np .…”

“…[7,8], structure (i.e., chain formation), magnetisation and volume changes due to application of an external uniform magnetic field depend on the type of uniaxial magnetic anisotropy of NPs. However, the above-cited works were focused exclusively on highly-filled samples with strong dipolar magnetic interaction between NPs.…”

Modeling the magnetostriction effect in elastomers with magnetically soft and hard particles

“…52 Numerous models use elastic springs to represent the mechanical constraints of the polymer matrix on the magnetic particles, either based on some fixed reference frame 33,35 or on an interconnected network of particles and springs. 45,47,48,50,[53][54][55] Explicit bead-spring monomer representations of the polymers, as the ones used in some models of magnetic gels, [56][57][58][59] still seem too expensive to provide useful insights on MEs. Another important simplification required by these models is the treatment of the magnetic properties of the embedded particles.…”