Structural characterization and magnetic properties of sol–gel derived Zn_xFe_3–xO₄ nanoparticles

Nanocrystalline Zn_xFe_3–xO₄ solid solutions (with x=0, 0.18, 0.45, 1) with crystallite sizes of 5–10 nm, specific surface of about 180 m²/g were synthesized via an inorganic variant of the sol–gel approach. The composition and structure of the formed nanoparticles were examined with the help of powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma atomic emission spectrometry and Fourier transform infrared spectroscopy. Hysteresis loops recorded for the samples indicate their ferromagnetic behavior at 5 K and superparamagnetic behavior at 300 K. The highest maximum magnetization of 59 emu/g at room temperature corresponds to Zn_0.18Fe_2.82O₄ composition, and at 5 K to Zn_0.45Fe_2.55O₄ (86 emu/g). The saturation magnetization of the pure magnetite was measured to be respectively 62 and 49 emu/g. - Highlights: • A modified inorganic sol–gel method was applied to prepare Zn_xFe_3–xO₄ nanoparticles. • Nanoparticles exhibit narrow size distribution with a particle size of 5–10 nm. • The compositions with a higher magnetization value than magnetite were obtained. • The synthesized Zn_xFe_3–xO₄ nanoparticles with x=0, 0.18, 0.45, 1 are superparamagnetic at room temperature