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https://doi.org/10.1007/s11664-020-08468-1  2020 The Minerals, Metals & Materials Society

Insight Into the Anomalous Electrical Behavior, Dielectric and Magnetic Study of Ag-Doped CoFe2O4 Synthesised by Okra Extract-Assisted Green Synthesis KRUTIKA L. ROUTRAY ,1,3 SUNIRMAL SAHA,2 and DHRUBANANDA BEHERA1 1.—Department of Physics and Astronomy, National Institute of Technology, Rourkela 769008, Odisha, India. 2.—C.V. Raman College of Engineering, Bhubaneswar 752054, India. 3.—e-mail: [email protected]

The effect of substitution of silver (Ag) on the structural, electric, dielectric and magnetic properties of nano-CoFe2O4 synthesized via green synthesis using okra plant extract is investigated. The lattice parameters and inverse spinel structure of Ag-substituted CoFe2O4 is confirmed from Rietveld refinement of the x-ray diffraction measurements, Fourier transform infrared (FT-IR) and Raman spectra. A lattice expansion is observed due to the incorporation of larger Ag ions into the CoFe2O4 lattice. Field emission scanning electron micrography analyses elucidate the formation of poly-faceted surfaces with reduction in particle size on Ag doping. The temperature dependent impedance and modulus study reveals the presence of relaxation phenomenon which is dependent on frequency and temperature. Frequency dependent dielectric measurements with increasing temperature obey the modified Debye model. Dielectric loss in the negative region for Ag-doped CoFe2O4 signifies the change of polarization direction due to an increase of Co2+/Fe2+ ratio for the substitution of Ag ions in the B site. Magnetic hysteresis curves exhibit a low field hysteresis loop at room temperature indicating the long-range ferromagnetic ordering nature of the samples. Low loss and high dielectric values make these materials a promising candidate for high frequency devices. Key words: Nanoferrite, microstructure, dielectric response, magnetic study

INTRODUCTION Owing to the remarkable electric, magnetic and dielectric properties, nano-spinel ferrites have attracted the interest of scientists. Such remarkable properties make these ferrites more captivating to nanoscience and nanotechnology.1–7 Among the spinel ferrites, cobalt ferrite (CFO) is found to have giant compositional variability by the incorporation of diverse cations in the parent lattice, and this disparity in cation distribution enhances the

(Received April 24, 2020; accepted September 2, 2020)

physical and chemical properties of the spinel ferrite.8 The large magneto-crystalline anisotropy and high value of saturation magnetism of CFO helps in understanding the suitability of the material in various applications. The magnetic properties of CFO are dependent on the site preference of the cation among the tetrahedral and octahedral sites and their compositions. Many researchers have reported about doping CFO with transition metals to enhance their properties.9–11 Taking this into account, addition of silver (Ag) to CFO enhances the properties as Ag is the most commercialized nan