A Novel Method for Obtaining Well-Separated Mn₃O₄ Nanocrystallites Deposited on the Surface of Spherical Silica

Manganese oxides have recently gained a lot of interest from scientists due to their unique structural, magnetic and optical properties, which make them favorable for diverse nanotechnological applications. Most applications, however, require stable and well-dispersed nanoparticles of nanometer size. Therefore, in this work, we show a procedure for obtaining separated crystallites of manganese oxide Mn3O4 on the surface of spherical silica carriers. The morphology and properties of nanoparticles were analyzed based on transmission electron microscopy observations, Raman spectroscopy, and low-temperature SQUID measurements. The analysis of results revealed the formation of well-dispersed Mn3O4 nanoparticles with an average size of approximately 9 nm. The magnetic measurements confirmed the characteristic critical temperature, and a narrow hysteresis loop appeared due to the surface anisotropy of nanoparticles. It was additionally demonstrated that such small nanoparticles possess pronounced nonlinear optical properties, as evidenced by strong signals of second and third harmonic generation. The obtained results fully confirmed the synthesis assumptions and offer promising prospects for the development of a new class of highly optically active manganese-based nanocomposites.