Preparation of cobalt substituted zinc ferrite nanopowders via auto-combustion route: an investigation to their structural and magnetic properties
CoxZn1−xFe2O4 (x = 0, 0.1, 0.2, 0.3, 0.4) nanopowders were fabricated via auto-combustion synthesis followed by calcined treatment. The structural, morphological, compositional and magnetic properties of the as-synthesized samples were decided by X-ray diffraction (XRD), field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, specific surface area and Physical Property Measurement System analyses, respectively. The XRD patterns revealed all annealed cobalt substituted zinc nanoferrites display a single phase cubic spinel structure, the decrease in lattice constant with increasing Co2+ ions concentration is related to the lattice shrinkage originated from the replacement of Zn2+ ions (ionic radii of 0.82 Å) by Co2+ ions (ionic radii of 0.78 Å); the increase of crystallite size with increasing Co2+ ions content can be attributed to the less exothermic for the formation of cobalt ferrite than that for zinc ferrite. The M–H curves revealed that there are unsaturated magnetization and negligible hysteresis loops for all samples with lower cobalt concentration (x = 0, 0.1, 0.2, and 0.3), implying a superparamagnetic behavior; while the Co0.4Zn0.6Fe2O4 nanoparticles (x = 0.4) show ferromagnetism at room temperature. The M–T relations inferred the substitution of cobalt ions can remarkably enhance Curie temperature of the as-prepared Co–Zn ferrite nanoparticles. At room temperature lower cobalt-substituted zinc nanoferrites tend to show superparamagnetism while higher cobalt-substituted zinc nanoferrites prefer to present ferromagnetism.
This work is supported by National Natural Science Foundation of China (No. 51571152), Research Fund for the Key Scientific Program of Higher Education of He’nan Province of China (No. 17B430006), Research fund of He’nan Provincial Training Program of Innovation and Entrepreneurship for Undergraduates (No. 201713503002), Research fund of Xinyang College Training Program of Innovation and Entrepreneurship for Undergraduates (No. CX20170003).
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