Evidence of Superparamagnetism in nano phased copper doped nickel zinc ferrites synthesized by Hydrothermal Method

Nanophased Ni0.65Zn0.35CuxFe(2-2x/3)O4, ferrites with lower dopant concentrations i.e., for x ranging from 0 to 0.05 in steps of 0.01 have been synthesized using hydrothermal route. Structural characterization is carried out by powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and far -IR spectroscopy (FTIR). XRD confirms the formation of pure spinel structure of Ni-Cu-Zn ferrites. Proposed cation distribution is able to explain properties of Cu2+ doped Ni-Zn ferrites. Variation of lattice constant a is explained through occupancy of dopant ions both in tetrahedral (A)-sites and octahedral (B)-sites. Crystallite size, determined for high intensity (3 1 1) peak using Debye-Scherrer method, W-H plots and Size-Strain plots, is found to exhibit an overall decreasing trend (62.75-31.56 nm) with x. Observed FTIR absorption bands at 400-600 cm(-1) confirm the formation of ferrite structure. Vibrating Sample magnetometer (VSM) studies reflect upon improved magnetic properties mainly due to adopted hydrothermal synthesis route, replacement of Fe3+ ions with very low dopant concentrations of Cu2+ ions of the order of 0.01%. Non-linear variation of M-s with x is attributed to Y-K angles and crystallite size. Highest value of M-s of 73.25 emu/gm is obtained for x = 0.02. Relatively higher values of M-s coupled with lower values of H (c) in nanophased Ni-Cu-Zn ferrites make them usable for high frequency and power applications. Lower values of coercivity (Hc) observed in the range of 32-80 Oe reveal the soft magnetic nature of these ferrites. Existence of single domain particles witnessed from variation of H-c with D indicate the superparamagnetic nature and confirms that these materials can be used for biomedical applications.

Automated summary

Nanophased Ni0.65Zn0.35CuxFe(2-2x/3)O4 ferrites with varying copper dopant concentrations were synthesized using a hydrothermal method, and their structural and magnetic properties were characterized. The results show that these ferrites exhibit improved magnetic properties and have potential applications in high frequency, power, and biomedical fields.