Cobalt doping on nickel ferrite nanocrystals enhances the micro-structural and magnetic properties: Shows a correlation between them

Abstract

In this paper, PVP capped nickel ferrite nanocrystals (NFN) and cobalt doped nickel ferrite nanocrystals (CNFN) have been prepared by thermal heat treatment method, followed by sintering at 700 °C. The synthesized nanocrystals have been analysed through XRD, TEM and SEM for their structural and morphological study. XRD analysis confirms the crystalline nature with cubic FCC lattice structure, whereas TEM and SEM study reveals the spherical morphology of the prepared nanocrystals with approximate average size of 21 nm and 24 nm for NFN and CNFN respectively. Also, the EDX spectra further confirms the incorporation of Co in the nickel ferrite nanocrystals (NFN) after doping. Further, Nelson-Riley plot has been used by considering error function to calculate the cubic lattice constant values and that are obtained as 0.835 nm and 0.841 nm respectively for NFN and CNFN. Most importantly, doping effect on microstructural properties have been analysed by considering Williamson-Hall (W-H) and Size-Strain Plot (SSP) method, and all these are then compared with that obtained from Halder-Wagner Method (H-W). Calculated average particle size from W-H, SSP and H-W method are found to match very well with that obtained from TEM and SEM analysis. Finally, magnetic parameters of NFN and CNFN have been studied by vibrating-sample magnetometer (VSM), where increase in saturation magnetization (Ms) from 19.97 emu/g to 26.93 emu/g and coercivity (Hc) value to 307 Oe has been observed with Co doping in NFN. The increase of such parameters has further been explained in terms of super exchange interaction between magnetic ions, total magnetic moments and magneto-crystalline anisotropic property, along with decrease in surface spin disorder and spin canting effect. Finally, a correlation between microstructural properties and magnetic properties has been observed. Such a good magnetic material (CNFN) may be used for the application of memory devices, magnetic recording media, and as good adsorbent for toxic materials like different dyes in water.