Nanocrystalline magnetite and Mn–Zn ferrite particles via the polyol process: Synthesis and magnetic properties

Abstract

Nanocrystalline Fe 3O 4 and Mn–Zn ferrite powders with crystallite sizes of 10 and 7 nm, respectively, and narrow size distribution were synthesized in a triethylene glycol medium. Mn–Zn ferrite particles with crystallite size of 9 and 12 nm were obtained after annealing of the as prepared ferrite particles at 300 and 500 °C, respectively. The saturation magnetization at 5 K of the Mn–Zn ferrite obtained at 300 °C (79 emu g −1) is smaller than that of the bulk material. Hysteresis loop measurements indicate ferrimagnetic behavior at 5 K and superparamagnetic behavior at 295 K. The Mn–Zn ferrite nanocrystals obtained at 500 °C, however, exhibit a smaller M s compared to the ferrite annealed at 300 °C indicating a change in the cation distribution.