Effects of Ce–Dy rare earths co-doping on various features of Ni–Co spinel ferrite microspheres prepared via hydrothermal approach

Almessiere M.A. Unal B. Slimani Y. Gungunes H. Toprak M.S. Tashkandi N. Baykal A. Sertkol M. Trukhanov A.V. Yıldız A. Manikandan A.
1 September 2021 Elsevier Editora Ltda

Journal of Materials Research and Technology
2021 #14 2534 - 2553 pp.

The effects of Ce–Dy co-doping on the crystal structure, optical, dielectric, magnetic properties, and hyperfine interactions of Ni–Co spinel ferrite microspheres synthesized hydrothermally have been studied. A series of ferrites with the general formula Ni_0.5Co_0.5Ce_xDy_xFe_2-2xO₄ were synthesized with x values ranging from 0.00 to 0.10. The phase, crystallinity, and morphology of ferrite microspheres were analyzed by X-ray powder diffractometry (XRD), scanning and transmission electron microscopes (SEM and TEM), respectively. The structural analyses of the synthesized ferrite microspheres confirmed their high purity and cubic crystalline phase. The Diffuse reflectance spectroscopic (DRS) measurements were presented to calculate direct optical energy band gaps (E_g) and is found in the range 1.63 eV - 1.84 eV. ⁵⁷Fe Mossbauer spectroscopy showed that the hyperfine magnetic field of tetrahedral (A) and octahedral (B) sites decreased with the substitution of Dy³⁺-Ce³⁺ ions that preferrentially occupy the B site. The impact of the rare-earth content (x) on the magnetic features of the prepared NiCo ferrite microspheres was investigated by analyzing M-H loops, which showed soft ferrimagnetism. The magnetic features illustrate a great impact of the incorporation of Ce³⁺-Dy³⁺ ions within the NiCo ferrite structure. The saturation magnetization (M_s), remanence (M_r), and coercivity (H_c) increased gradually with increasing Ce–Dy content. At x = 0.04, M_s, M_r, and H_c attain maximum values of about 31.2 emu/g, 11.5 emu/g, and 512.4 Oe, respectively. The Bohr magneton (n_B) and magneto-crystalline anisotropy constant (K_eff) were also determined and evaluated with correlation to other magnetic parameters. Further increase in Ce³⁺-Dy³⁺ content (i.e., x ≥ 0.06) was found to decrease M_s, M_r, and H_c values. The variations in magnetic parameters (M_s, M_r, and H_c) were largely caused by the surface spins effect, the variations in crystallite/particle size, the distribution of magnetic ions into the different sublattices, the evolutions of magneto-crystalline anisotropy, and the variations in the magnetic moment (n_B). The squareness ratios were found to be lower than the predicted theoretical value of 0.5 for various samples, indicating that the prepared Ce–Dy substituted NiCo ferrite microspheres are composed of NPs with single-magnetic domain (SMD). Temperature and frequency-dependent electrical and dielectric measurements have been done to estimate the ac/dc conductivity, dielectric constant, and tangent loss values for all the samples. The ac conductivity measurements confirmed the power-law rules, largely dependent on Ce–Dy content. Impedance analysis stated that the conduction mechanisms in all samples are mainly due to the grains-grain boundaries. The dielectric constant of NiCo ferrite microspheres give rise to normal dielectric distribution, with the frequency depending strongly on the Ce–Dy content. The observed variation in tangential loss with frequency can be attributed to the conduction mechanism in ferrites, like Koops phenomenological model.

Conductivity , Dielectric properties , Ferrimagnetic , Ferrite microsphere , Hyperfine interaction , NiCo spinel ferrites

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Department of Physics, College of Science, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam, 31441, Saudi Arabia
Department of Biophysics, Institute for Research and Medical Consultations (IRMC), Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam, 31441, Saudi Arabia
Institute of Forensic Sciences & Legal Medicine, Istanbul University–Cerrahpaşa, Buyukcekmece Campus, Buyukcekmece, Istanbul, 34500, Turkey
Department of Physics, Hitit University, Çevre Yolu Bulvarı, Çorum, 19030, Turkey
Department of Applied Physics, KTH-Royal Institute of Technology, Stockholm, SE10691, Sweden
Department of Nanomedicine Research, Institute for Research and Medical Consultations (IRMC), Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam, 31441, Saudi Arabia
Department of Basic Science, Deanship of Preparatory Year and Supporting Studies, Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam, 34212, Saudi Arabia
Scientific-Practical Materials Research Centre of NAS of Belarus, P. Brovki Str., 19, Minsk, 220072, Belarus
South Ural State University, Lenin Av., 76, Chelyabinsk, 454080, Russian Federation
L.N. Gumilyov Eurasian National University, 2, Satpayev Str., Nur-Sultan, 010000, Kazakhstan
Namik Kemal University, Çorlu Engineering Faculty, Textile Engineering Department, Çorlu-Tekirdag, 59860, Turkey
Department of Chemistry, Bharath Institute of Higher Education and Research (BIHER), Bharath University, Chennai, 600 073, Tamil Nadu, India
Center for Catalysis and Renewable Energy, Bharath institute of Higher Education and Research (BIHER), Chennai, 600 073, Tamil Nadu, India

Department of Physics
Department of Biophysics
Institute of Forensic Sciences & Legal Medicine
Department of Physics
Department of Applied Physics
Department of Nanomedicine Research
Department of Basic Science
Scientific-Practical Materials Research Centre of NAS of Belarus
South Ural State University
L.N. Gumilyov Eurasian National University
Namik Kemal University
Department of Chemistry
Center for Catalysis and Renewable Energy

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