This work is devoted to the theoretical study of the structural and magnetic properties of an ensemble of single-domain interacting magnetic nanoparticles immobilized in a non-magnetic medium. This model is typical for describing magnetically active soft materials, “smart” polymer ferrocomposites, which have been applied in science-intensive industrial and biomedical technologies. It is assumed that the ferrocomposite is obtained by solidification of the carrier medium in a ferrofluid under an external magnetic field, the intensity of which is determined by the Langevin parameter α_p; after the solidification of the carrier liquid, the nanoparticles retain the spatial distribution and orientation of their easy magnetization axes. The features of the orientational texture formed in the sample are analyzed depending on the intensity of the magnetic field α_p and interparticle dipole–dipole interactions. The magnetization of a textured ferrocomposite in the magnetic field α is also investigated. Our results show that in the case of a co-directional arrangement of the considered fields and if α < α_p, the ferrocomposites are magnetized much more efficiently than ferrofluids due to their texture. In the fields α > α_p, the ferrocomposite is magnetized less efficiently than the ferrofluid due to the internal magnetic anisotropy of the nanoparticles. The analytical expressions presented here make it possible to predict the magnetization of a ferrocomposite depending on its internal structure and synthesis conditions, which is the theoretical basis for the synthesis of ferrocomposites with a predetermined magnetic response in a given magnetic field.

中文翻译：

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磁活性铁复合材料的结构和磁化强度

这项工作致力于对固定在非磁性介质中的单畴相互作用磁性纳米粒子集合的结构和磁性进行理论研究。该模型是描述磁活性软材料、“智能”聚合物铁复合材料的典型模型，已应用于科学密集型工业和生物医学技术。假设铁复合材料是通过在外磁场下铁磁流体中的载体介质固化获得的，其强度由朗之万参数α _p确定; 载液固化后，纳米粒子保持其易磁化轴的空间分布和取向。根据磁场α _p的强度和粒子间偶极-偶极相互作用来分析样品中形成的取向织构的特征。还研究了在磁场α中织构铁复合材料的磁化强度。我们的结果表明，在所考虑的场的同向排列的情况下，如果α < α _p，由于其质地，铁复合材料的磁化效率比铁磁流体高得多。在领域α > α _p，由于纳米颗粒的内部磁各向异性，铁复合材料的磁化效率低于铁磁流体。这里提出的解析表达式可以根据铁复合材料的内部结构和合成条件预测其磁化强度，这是在给定磁场中合成具有预定磁响应的铁复合材料的理论基础。