The effect of Zn2+ substitution on magnetic properties of maghemite nanoparticles, prepared by one-pot coprecipitation method at room temperature

Abstract

In this work, Zn2+-substituted maghemite (γ-Fe2(1−x/3 ) ZnxO3, x = 0.0, 0.1, 0.2, 0.3 and 0.4) nanoparticles were synthesized via one-pot coprecipitation method at room temperature. Their structural and magnetic properties were studied by X-ray diffraction (XRD), magnetic thermogravimetry (TG/M/), vibrating sample magnetometry (VSM) and Fourier transform infrared (FTIR) spectroscopy methods. XRD analysis shows that all as-prepared samples have a spinel structure and their lattice constants change from 8.334 to 8.391 Å, depending on the Zn2+ content. Mean crystallite sizes of the as-prepared nanoparticles were estimated by Scherrer’s formula, which are between 3.4 and 4.9 nm. FTIR analysis reconfirms maghemite phase formation. Curie temperature of the samples was determined under two different conditions, one in uncapsulated form and another one in vacuumed quartz capsule, using TG/M/ method. The results show that the Curie temperature of the samples, measured in the uncapsulated form, is decreased from 515 to 330 °C as Zn2+ content increases. Also Curie temperature of the capsulated samples exhibits a reduction from 580 to 280 °C. Room-temperature magnetic measurements illustrate that as Zn2+ content increases, saturation magnetization initially increases from 53 emu/g to 54 emu/g for x = 0.1 and then decreases to 42 emu/g. These variations were discussed based on A and B sites occupations by diamagnetic and paramagnetic ions and reduction in A–A, B–B and A–B superexchange interactions, as a result of both increase in lattice constant and presence of more diamagnetic Zn2+ ions in the structure. These nanoparticles are suitable for fabrication of Faraday rotation devices potentially. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.