In this research work we study the influence of Co doping on structural, optical, dielectric and magnetic properties of γ-Fe2O3 (maghemite), which is synthesized by chemical co-precipitation process. The inverse spinel structure of γ-Fe2O3 and Co (5 wt%) doped γ-Fe2O3 nanoparticles is confirmed by X-ray Diffraction (XRD), Fourier transform Infrared and Raman techniques. The average particle size is calculated, using Transmission electron microscope is about 10.83 ± 1.83 nm and 14.76 ± 2.41 nm for undoped and Co doped maghemite nanoparticles respectively, also confirmed by XRD measurements. The introduction of Co to γ-Fe2O3 nanoparticles improves crystallization. The dielectric measurement (ϵr, tanδ) gives the deep insight of the microstructure of the samples. The dielectric constant (ϵr) reduced in case of Co doped γ-Fe2O3 nanoparticles, which is more likely due to reduction in defect density and enhancement in grain size and crystallization by introduction of Co into γ-Fe2O3 lattice. The enhancement in ac conductivity (σac) in case of Co doped γ-Fe2O3 is due to fast hopping process between Fe2+/Fe3+ in undoped maghemite, increase in conducting grain volume and charge density (detached from traps + conducting charge carriers) in Fe2+/Fe3+ and Co2+/Co3+ in doped maghemite nanoparticles. The blocking temperature shifted from 62 to 88 K, which is most possibly due to increased grain size, enhanced interaction of dipole–dipole and probably increase the potential barrier for thermal instabilities. Both samples show superparamagnetic characteristic and the saturation magnetization (Ms) is increased from 30 to 35 emu/g in case of Co doped maghemite nanoparticles. This is due to Co and lattice spins parallel alignment in maghemite nanoparticles.
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This work is done by the support Higher Education Commission of Pakistan (HEC) under START-UP RESEARCH GRANT PROGRAM abbreviated as SRGP with Grant Nos 21-1732/SRGP/R&D/HEC/2017 and 21-1553/SRGP/R&D/HEC/2017, the Fundamental Research Funds for the HEC Pakistan. Higher Education Research Endowment Fund by Khyberpukhtunkhwa (KP) Government Grant No. PMU1-22/HEREF/2014–2015/Vol/IV-.
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Hussain, M., Khan, R., Zulfiqar et al. Dielectric and magnetic properties of cobalt doped γ-Fe2O3 nanoparticles. J Mater Sci: Mater Electron 30, 13698–13707 (2019). https://doi.org/10.1007/s10854-019-01747-6