Magnetic interactions between nanoparticles

We present a short overview of the influence of inter-particle interactions on the properties of magnetic nanoparticles. Strong magnetic dipole interactions between ferromagnetic or ferrimagnetic particles, that would be superparamagnetic if isolated, can result in a collective state of nanoparticles. This collective state has many similarities to spin-glasses. In samples of aggregated magnetic nanoparticles, exchange interactions are often important and this can also lead to a strong suppression of superparamagnetic relaxation. The temperature dependence of the order parameter in samples of strongly interacting hematite nanoparticles or goethite grains is well described by a simple mean field model. Exchange interactions between nanoparticles with different orientations of the easy axes can also result in a rotation of the sub-lattice magnetization directions.

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Particle Orientational Properties and Viscosity of a Dense Colloidal Dispersion Composed of Ferromagnetic Spherocylinder Particles: Analysis by Means of Mean Field Approximation for a Simple Shear

Fluids Engineering ◽

10.1115/imece2005-79226 ◽

2005 ◽

Author(s):

Akira Satoh

Keyword(s):

Magnetic Field ◽

Applied Magnetic Field ◽

Mean Field ◽

Magnetic Interaction ◽

Colloidal Dispersion ◽

Field Approximation ◽

Magnetic Interactions ◽

Mean Field Approximation ◽

Particle Interactions ◽

Orientational Distribution

We have theoretically investigated the particle orientational distribution and viscosity of a dense colloidal dispersion composed of ferromagnetic spherocylinder particles under circumstances of an applied magnetic field. The mean field approximation has been applied to take into account the magnetic interactions of the particle of interest with the other ones which belong to the neighboring clusters, besides its own cluster. The basic equation of the orientational distribution function, which is an integro-differential equation, has approximately been solved by Galerkin’s method and the method of successive approximation. Even when the magnetic interaction between particles is of the order of the thermal energy, the effect of particle-particle interactions on the orientational distribution comes to appear more significantly with increasing the volumetric fraction of particles. This effect comes to appear more significantly when the influence of the applied magnetic field is not relatively so strong compared with magnetic particle-particle interactions.

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Cluster mean-field model of the spin glasses: static properties

Physical Review B ◽

10.1103/physrevb.18.1439 ◽

1978 ◽

Vol 18 (3) ◽

pp. 1439-1445 ◽

Cited By ~ 48

Author(s):

C. M. Soukoulis ◽

K. Levin

Keyword(s):

Spin Glasses ◽

Field Model ◽

Mean Field ◽

Static Properties ◽

Mean Field Model

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External Environment Dependent Spin and Orbital Exchange Interactions

Journal of Modeling and Simulation of Materials ◽

10.21467/jmsm.3.1.79-83 ◽

2020 ◽

Vol 3 (1) ◽

pp. 79-83

Author(s):

Eunsung Jekal

Keyword(s):

Mean Field Theory ◽

Mean Field ◽

External Environment ◽

Exchange Interactions ◽

Electronic System ◽

Dipole Interaction ◽

Spin Model ◽

Magnetic Interactions ◽

Anisotropic Exchange ◽

Moriya Interaction

We present a set of equations expressing the parameters of the magnetic interactions of an electronic system. This allows to establish a mapping between the initial electronic system and a spin model including up to quadratic interactions between the effective spins, with a general interaction (exchange) tensor that accounts for anisotropic exchange, Dzyaloshinskii–Moriya interaction and other symmetric terms such as dipole–dipole interaction. We present the formulas in a format that can be used for computations via Dynamical Mean Field Theory algorithms.

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