Abstract
The bismuth (Bi3+)-doped cobalt ferrite nanostructures with dual phase, i.e. cubic spinel with space group Fd3m and perovskite with space group R3c, have been successfully engineered via self-ignited sol-gel combustion route. To obtain information about the phase analysis and structural parameters, like lattice constant, Rietveld refinement process is applied. The replacement of divalent Co2+ by trivalent Bi3+ cations have been confirmed from energy dispersive analysis of the ferrite samples. The micro-structural evolution of cobalt ferrite powders at room temperature under various Bi3+ doping levels have been identified from the digital photoimages recorded using scanning electron microscopy. The hyperfine interactions, like isomer shift, quadrupole splitting and magnetic hyperfine fields, and cation distribution are confirmed from the Mossbauer spectra. Saturation magnetization is increased with Bi3+-addition up to x = 0.15 and then is decreased when x = 0.2. The coercivity is increased from 1457 to 2277 G with increasing Bi3+-doping level. The saturation magnetization, coercivity and remanent ratio for x = 0.15 sample is found to be the highest, indicating the potential of Bi3+-doping in enhancing the magnetic properties of cobalt ferrite.
Highlights
Structural and chemical composition of multi-component inorganic nanostructures have stimulated technological and scientific interest to alter the physiochemical properties while developing magnetic, electric, catalysis, and spintronic devices[1,2,3,4,5,6]
The crystal structure and phase transition of the samples were confirmed from the X-ray powder diffraction (XRD) patterns
In accordance with JCPDS card no. 20–0169 with space group-R3c31, occurrence of an additional (101) and (110) reflection planes for x ≥ 0.10 Bi3+-doping level corroborates the existence of BiFeO3
Summary
The bismuth (Bi3+)-doped cobalt ferrite nanostructures with dual phase, i.e. cubic spinel with space group Fd3m and perovskite with space group R3c, have been successfully engineered via self-ignited sol-gel combustion route. Bismuth ferrite (BiFeO3) has been reported as one of the versatile cubic perovskites exhibiting both ferroelectricity and G-type anti-ferromagnetism above room temperature[17, 18] In multiferroics, parameters such as electric polarization and magnetism generally are responsible for magnetoelectric effect[19]. Due to special structural features dual phase materials demonstrate different magnetic and electric properties. We report on the synthesis of dual phase Bi3+-doped CoFe2O4 nanostructures with general formula Co1−xBixFe2O4 (CBF) where x = 0.0–0.2 by sol-gel self-combustion method. For the qualitative evaluation of the Mossbauer spectra recoil spectra were analyzed using WinNormosFIT software[29]
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