Controllable synthesis and magnetothermal properties of Zn_0.3Fe_2.7O₄ nanoparticles

The octahedral, decahedral and star-like Zn_0.3Fe_2.7O₄ nanoparticles were prepared by changing the heating rate, using 4-biphenyl carboxylic acid as a surfactant in the high temperature organic thermal decomposition synthesis, achieving controllable synthesis of nanoparticles morphology growth. Using the reverse microemulsion method, nanoparticles were coated with SiO₂ of different shell thicknesses, making them water-soluble, and the specific loss power (SLP) of Zn_0.3Fe_2.7O₄@SiO₂ composite nanoparticles under an alternating magnetic field was studied. The results indicate that the heat generation capacity of the nanoparticles decreases with increasing SiO₂ shell thickness under high magnetic fields, while it increases with increasing SiO₂ shell thickness under low magnetic fields. As the SiO₂ thickness increases, the dipolar interactions between the magnetic nanoparticles are reduced, leading to a decrease in the resulting anisotropy. This causes SLP of the magnetic nanoparticles to exhibit different rules under high and low magnetic fields.