Magnetic ferrites synthesised using the microwave-hydrothermal method

Ceramic spinel-based ferrites of Cobalt, Nickel, Copper and Zinc were prepared using the hydrothermal method assisted with microwave. All samples were characterised using EDS, WDXRF, XRD, SEM, FTIR, Raman and VSM techniques. The structural, compositional, phonic and magnetic properties indicate that the evaluated method can produce magnetic materials. The EDS and WDXRF analyses suggest the materialisation of Co1.0Fe2.0O4, Ni0.9Fe2.1O4, Cu1.1Fe1.9O4 and Zn1.1Fe1.9O4 ferrites. XRD measurements indicate the formation of monophasic Cobalt, Nickel and Zinc cubic inverse-spinel-based structures, whereas Cooper ferrite was structured as body-centred tetragonal distorted inverse-spinel and cubic phase, which was contaminated with monoclinic CuO. The estimated average crystallite sizes using Rietveld refinement were approximately 163 nm (Co1.0Fe2.0O4), 187 nm (Ni0.9Fe2.1O4), 21 nm (Cu1.1Fe1.9O4) and 226 nm (Zn1.1Fe1.9O4). Infrared spectra exhibit characteristic modes at approximately 574-581 cm−1 [ν(Co-O)]Td, 568-603 cm−1 [ν(N-O)]Td, 607-661 cm−1 [ν(Cu-O)]Td and 578-598 cm−1 [ν(Zn-O)]Td. The Raman spectra for Co1.0Fe2.0O4 exhibit vibrational modes at 172 (T2g), 304 (Eg) 460 (A1g) and 620-680 cm−1 (A1g), whereas Ni0.9Fe2.1O4 exhibits T2g (477 cm−1) A1g (690 cm−1) modes. Cu1.1Fe1.9O4 shows vibrational modes at approximately 148 (F2g), 447 (F2g), 552 (F2g) and 671 cm−1 (A1g), and Zn1.1Fe1.9O4 has another four distinct modes at approximately 248, 348, 486 and 651, which are assigned to Eg, T2g and A1g symmetries. Several obtained ferrites exhibit soft magnetisation with ferromagnetic (Co1.0Fe2.0O4, Ni0.9Fe2.1O4 and Cu1.1Fe1.9O4) and paramagnetic (Zn1.1Fe1.9O4) characteristics.