The effect of yttrium substitution on the magnetic properties of magnetite nanoparticles

• Single phase yttrium substituted magnetite nanoparticles were synthesized by hydrothermal-reduction route.
• Citric acid plays a key role in reduction of Fe3+ to Fe2+, which is necessary for the formation of magnetite phase.
• It is possible to substitute yttrium ions for iron ones as high as x=0.4 by hydrothermal reduction route.
• Pure magnetite nanoparticles prepared by this route has a high saturation magnetization.
• Yttrium substituted magnetite nanoparticles are superparamagnet at room temperature.

Superparamagnetic Y-substituted magnetite (YxFe3–xO4,with x=0.00, 0.10, 0.15, 0.20 and 0.40) nanoparticles were synthesized via hydrothermal reduction route in the presence of citric acid. The synthesized nanoparticles were characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), vibrating sample magnetometry (VSM) and gradient field thermomagnetic measurement. The results showed that a minimum amount of citric acid is required to obtain single phase Y-substituted magnetite nanoparticles. Citric acid acts as a modulator and reducing agent in the formation of spinel structure and controls nanoparticle size and crystallinity. Mean crystallite sizes of the single-phase powders were estimated by Williamson–Hall method. Curie temperature measurement of the samples shows that as yttrium content increases, the Curie temperature decreases. Magnetic measurements show that the saturation magnetization of the samples decreases as x increases up to 0.15 and then increases to x=0.20 and finally decreases again for x=0.40.