© 2018 The Author(s). Currently, superparamagnetic functionalized systems of magnetite (Fe3O4) nanoparticles (NPs) are promising options for applications in hyperthermia therapy, drug delivery and diagnosis. Fe3O4NPs below 20 nm have stable single domains (SSD), which can be oriented by magnetic field application. Dispersion of Fe3O4NPs in silicon dioxide (SiO2) matrix allows local SSD response with uniaxial anisotropy and orientation to easy axis, 90° <001> or 180° <111>. A successful, easy methodology to produce Fe3O4NPs (6-17 nm) has been used with the Stöber modification. NPs were embedded in amorphous and biocompatible SiO2matrix by mechanical stirring in citrate and tetraethyl orthosilicate (TEOS). Fe3O4NPs dispersion was sampled in the range of 2-12 h to observe the SiO2matrix formation as time function. TEM characterization identified optimal conditions at 4 h stirring for separation of SSD Fe3O4in SiO2matrix. Low magnetization (Ms) of 0.001 emu and a coercivity (Hc) of 24.75 Oe indicate that the embedded SSD Fe3O4in amorphous SiO2reduces the Msby a diamagnetic barrier. Magnetic force microscopy (MFM) showed SSD Fe3O4of 1.2 nm on average embedded in SiO2matrix with uniaxial anisotropy response according to Fe3+and Fe2+electron spin coupling and rotation by intrinsic Neél contribution.
Fuentes-García, J. A., Diaz-Cano, A. I., Guillen-Cervantes, A., & Santoyo-Salazar, J. (2018). Magnetic domain interactions of Fe<inf>3</inf>O<inf>4</inf>nanoparticles embedded in a SiO<inf>2</inf>matrix. Scientific Reports. https://doi.org/10.1038/s41598-018-23460-w