Silica matrix-driven modulation of ferrite nanoparticles: Insights into synthesis, coercivity and magnetization

Abstract

This study introduces a thermal decomposition synthesis method to synthesize bare and embedded cobalt ferrite nanoparticles in a silica matrix, enabling a direct comparison between them to examine agglomeration and particle size effects on magnetic properties. XRPD confirmed the cubic spinel structure, with reduced crystallinity in the composite due to the amorphous silica. FTIR analysis verified CoFe₂O₄ incorporation into silica, showing metal–oxygen (560–410 cm⁻¹) and Si–O–Si (1030 cm⁻¹) bonds. TEM revealed agglomerated particles (≈30 nm) in bare CoFe₂O₄, whereas the composite exhibited smaller (≈20 nm), dispersed nanoparticles within the silica. The XPS spectra confirm that the Fe and Co ions in both samples exhibit oxidation states of Fe³⁺ and Co²⁺. Magnetic characterization showed contrasting behaviors: bare CoFe₂O₄ exhibited higher coercivity at 300 K (1509 Oe) but lower at 5 K (7172 Oe) compared to the composite (1073 Oe and 8407 Oe, respectively). These trends were linked to particle size distributions, with the silica matrix promoting smaller superparamagnetic nanoparticles and reduced inter-particle interactions. These behaviors are driven by the interplay between superparamagnetic and ferrimagnetic nanoparticle populations. The silica plays a key role in controlling particle size, agglomeration and magnetic properties, offering insights into tailoring nanocomposites for data storage, biomedicine, and catalysis. Future work should optimize cobalt ferrite weight percentages in the silica matrix to achieve control over particle size and agglomeration.