Synthesis, analysis and characterization of structural, magnetic and dielectric properties of Ni sub(x)Co sub(1-x)Fe sub(2)O sub(4), (0.0 less than or equal to x less than or equal to 1.0) ferrite nanoparticles with change in Ni concentration

Abstract

Magnetic materials are utilized across a broad spectrum of applications within the contemporary technological and medical sectors. These materials are generally synthesized by solid-state synth)es sub(i- )me sub(t)h sub(o)d that involves prolonged and high temperature heating. Developing -ynthesis strategies to obtain these materials not just in single phase but also under milder heating conditions is a task for researchers. Nickel-doped cobalt ferrite is a well-known magnetic material. Our study reports the synthesis of a series of nanocrystalline Ni-doped Co ferrite nanoparticles with the composition Ni sub(x)Co sub(1-x)Fe sub(2)O sub(4) (x ranging from 0.0 to 1.0) that were synthesized via a simple low-temperature precursor combustion synthesis method followed by a sintering step. The sintered ferrites were characterized to determine their purity by X-ray diffraction, Infrared spectroscopy and Raman Spectroscopy. XPS analysis gave the oxidation state of the different metal cations and their site occupancy. The magnetic, dielectric and conductivity properties of the ferrites were studied and correlated to the Ni dopant concentration. Diffraction analysis revealed that the ferrites were composed of single and highly crystalline cubic spinel unit cells belonging to the space group Fd-3 m. The variation in the nickel content impacts the structural, magnetic and dielectric properties of the ferrite. As the Ni content in the ferrite solid solution was increased, the dimensions of the unit cell of the sintered ferrites decreased. Observations of the two fundamental bands within the wavenumber range of 400-630 cm-1 in the Infrared spectrum, along with the four bands corresponding to the E sub(g), T sub(2g)(2), T sub(2g)(3) and A sub(1g) modes in Raman spectra, validated the formation of the spinel cubic unit cell. The lower frequency band in the Infrared spectrum shows a split with increase in Ni content, indicating a shift from a normal to an inverse spinel structure with increase in Ni content. SEM images show a cuboidal particle shape aggregation formed by the particles. The XPS analysis showed that cobalt and nickel are in the+2-oxidation state, while iron is present as Fe sup(3+). XPS also concurred with the FTIR analysis that a change from normal to inverse spinel take place with increase in Ni doping. The magnetization data showed that ferrite properties are influenced by the concentration of divalent metal cations, with coercivity decreasing from 815 Oe in CoFe sub(2)O sub(4) to 49 Oe in NiFe sub(2)O sub(4). The ferrite with the highest concentration of cobalt showed the highest saturation magnetization. The Curie temperature increased with increase in the nickel content. The decrease in dielectric constant and dielectric loss is dependent on frequency, with both parameters decreasing as frequency increases. The simple nature of the synthesis process, the stability and single-phase material coupled with its magnetic properties make it an interesting material that can be used in near future.