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Published on: June 7, 2018
Effect of Cr3+ doping on Co-Mg spinel ferrites: structural, high-temperature dielectric, optical, and magnetic
Sunil Kumawat1, Anuradha1, Vishnu Sen1
1Department of Physics, Mohanlal Sukhadia University Udaipur 313001 Rajasthan India gunjan.arora@mlsu.ac.in.
Abstract:
Co0.6Mg0.4Cr x Fe2-x O4 (x = 0.0-0.4) spinel ferrites are successfully synthesized via a sol-gel route to explore the influence of Cr3+ substitution on their multifunctional properties. Rietveld refined PXRD patterns confirm the formation of a single-phase cubic spinel structure with crystallite sizes of ∼17-22 nm. The incorporation of Cr3+ ions, verified through HRTEM, FTIR, Raman, and XPS analyses, leads to lattice contraction due to the smaller ionic radius compared to Fe3+. Dielectric and impedance studies revealed Maxwell-Wagner interfacial polarization along with non-Debye type relaxation behavior, accompanied by a negative temperature coefficient of resistance. The frequency-dependent AC conductivity follows Jonscher's power law, indicating a thermally activated small polaron hopping conduction mechanism with activation energies in the range of 0.46-0.69 meV. Optical studies demonstrate a systematic increase in the band gap from 2.17 to 3.12 eV with increasing Cr3+ content, attributed to modification in M-O bonding. Magnetic measurements exhibit soft ferromagnetic behavior, with a reduction in saturation magnetization (54.74 to 29.53 emu g-1) and coercivity (998 to 317 Oe), primarily governed by weaker A-B super-exchange interactions and stronger spin canting. These properties indicate that the materials hold potential for capacitive and photocatalytic applications.
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