Department of Physics, Building 307; Technical University of Denmark; DK-2800 Kongens Lyngby; Denmark.
Beilstein J Nanotechnol. 2010;1:182-90. doi: 10.3762/bjnano.1.22. Epub 2010 Dec 28.
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.
我们简要介绍了颗粒间相互作用对磁性纳米粒子性能的影响。如果孤立存在，铁磁或亚铁磁粒子之间的强磁偶极相互作用会导致纳米粒子的集体状态。这种集体状态与自旋玻璃有许多相似之处。在聚集的磁性纳米粒子样品中，交换相互作用通常很重要，这也会导致超顺磁弛豫的强烈抑制。强相互作用的赤铁矿纳米粒子或针铁矿颗粒样品中有序参数的温度依赖性可以很好地用简单的平均场模型来描述。具有不同易轴方向的纳米粒子之间的交换相互作用也会导致子晶格磁化方向的旋转。
