Effect of Mn²⁺ doping and SiO₂ coating on magneto-optical properties of CoFe₂O₄ nano-particles

Abstract

Co 1− x Mn x Fe 2 O 4 ( x = 0.2, 0.4, 0.6, 0.8, 1.0) magnetic nanoparticles were prepared using a modified citrate gel method and fired at 500 °C for 2 h. The modified Stöber method was used for coating the magnetic nanoparticles with a silica shell. The effects of Mn 2+ substitution and the method of preparation on the formation of crystalline phases, particle size, morphology and the optical and magnetic properties of the synthesized materials were investigated by XRD, SAED, HR-TEM, EDX, UV/VIS double-beam spectrophotometry and vibrating sample magnetometry. The average crystallite size of the synthesized nanoparticles was 18.6–43.9 nm. The maximum value of saturation magnetization (Ms) achieved was 65.668 emu/g for Mn 0.2 Co 0.8 Fe 2 O 4 nanoparticles. Diffuse reflectance increased with an increase of Mn 2+ content and SiO 2 shell. These coated magnetic nanoparticles are promising materials for application to magnetic sensors and biomedical nanodevices.