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Cation distributions and magnetism of Al-substituted CoFe2O4 - NiFe2O4 solid solutions synthesized by sol-gel auto-combustion method

Kumar, Vijaya R and Anupama, AV and Kumar, R and Choudhary, Harish Kumar and Khopkar, VB and Aravind, G and Sahoo, B (2018) Cation distributions and magnetism of Al-substituted CoFe2O4 - NiFe2O4 solid solutions synthesized by sol-gel auto-combustion method. In: CERAMICS INTERNATIONAL, 44 (17). pp. 20708-20715.

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Official URL: http://dx.doi.org/10.1016/j.ceramint.2018.08.065

Abstract

Aluminium substituted cobalt-nickel ferrite nanoparticles were synthesized by citrate gel auto-combustion method followed by annealing at 1000 degrees C for 1 h in air. Scanning electron micrographs of all the samples show crystalline particles of irregular morphology with a small variation in particle sizes (similar to 110-160 nm). From the analysis of the X-ray diffraction results we observed that the unit cell parameter decreases linearly with increase in aluminium concentration due to the smaller ionic radius of the Al3+ ions substituting the other cations such as Co2+, Ni2+ and Fe3+ ions in the compounds. The room temperature Mossbauer spectra of the samples show Zeeman split sextet patterns corresponding to the tetrahedral (Th) and octahedral (Oh) interstitial iron (Fe3+) cations. The observed magnetic hyperfine field (B-hf) decreases with increase in Al-concentration due to the distribution of diamagnetic Al3+ in the environment of Fe-57 probe atoms. The saturation magnetization measured by Vibrating Sample Magnetometer (VSM) shows a similar trend like that of Bhf. The distributions of the cations obtained from the Rietveld refinement and Mossbauer spectroscopy results indicate an increase in Fe3+(Th)/Fe3+ (Oh) occupancy-ratio on increasing Al3+ concentration, and Ni-2 cations prefer the octahedral site, whereas Co-2 and Al3+ ions redistribute themselves in tetrahedral and octahedral sites, in the ratio 2:3.

Item Type: Journal Article
Additional Information: Copy right for this article belong to ELSEVIER SCI LTD
Keywords: Citrate-gel auto-combustion method; Al-doped Co-Ni ferrites; Mossbauer spectroscopy; Rietveld refinement; Magnetic properties
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Depositing User: Id for Latest eprints
Date Deposited: 19 Nov 2018 14:42
Last Modified: 01 Mar 2019 09:25
URI: http://eprints.iisc.ac.in/id/eprint/61095

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