Synthesis and Mössbauer study of anomalous magnetic behavior of Fe2O3 nanoparticle-montmorillonite nanocomposites

In ensembles of single-domain magnetic nanoparticles, a magnetic-dipole interaction between particles takes place. The controlled assembly of bulk magnetically ordered materials from such nanoparticles opens up wide prospects for the creation of new magnetic materials. One of the classical methods for obtaining an ordered ensemble of nanoparticles is their synthesis in a matrix of clay minerals such as montmorillonite. The interlayer space of the mineral acts as a nanoreactor with specific conditions for the particle synthesis. Intercalating iron polycations into montmorillonite, one can obtain well-ordered ensembles of magnetic nanoparticles. Magnetic nanocomposites created in this way have new properties and exhibit non-standard magnetic behavior, which cannot always be described in terms of classical concepts. We used the capabilities of Mössbauer relaxation spectroscopy to study magnetic nanocomposites in order to study the structural and magnetic features of nanoparticles formed in aluminosilicate layers “from the inside”. An analysis of the Mössbauer spectra revealed that ordered ensembles of antiferromagnetic α-Fe2O3 nanoparticles formed between aluminosilicate layers of montmorillonite exhibited ferromagnetic behavior.