title: Magnetic interactions between nanoparticles.
abstract: 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.
authors: Department of Physics, Building 307; Technical University of Denmark; DK-2800 Kongens Lyngby; Denmark.
authors: Steen
authors: S
authors: Mørup
authors: Mikkel Fougt
authors: MF
authors: Hansen
authors: Cathrine
authors: C
authors: Frandsen