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Cation Distribution Dependent Magnetic Properties in CoCr2-xFexO4 (x= 0.1 to 0.5): EXAFS, Mӧssbauer and Magnetic Measurements

Abstract

In this report, we have examined the evolution of structure and rich magnetic transitions such as paramagnetic to ferrimagnetic phase at Curie temperature (TC), spiral ordering temperature (TS) and lock-in temperature (TL) observed in CoCr2O4 spinel multiferroic after substituting Fe. The crystal structure, microstructure and cation distribution among the tetrahedral (A) and octahedral (B) sites in the spinel lattice are characterised by X-ray diffraction, Transmission Electron Microscopy, Extended X-ray Absorption Fine Structure (EXAFS) and Mӧssbauer spectroscopy. Due to same radial distances of the first coordination shell in both tetrahedral and octahedral environments observed in EXAFS spectra, the position of second coordination shell specifies the preference of more Fe ions towards the A site at x= 0.1. At x= 0.5, Fe ions favour more the B site. The cation distribution quantitatively obtained from the Mӧssbauer spectral analysis shows that 60% and 40% of Fe ions while occupy the A site in x= 0.1 and 0.5 respectively, surprisingly at x= 0.3, Fe ions are distributed equally among the A and B sites. The dc magnetization reveals an increase in TC from 102 K to 200 K and TS from 26 to 40 K with increase in Fe concentration indicating an enhancement in A-B exchange interaction at the expense of B-B. No report so far demonstrates such enhancement in TS either in pure or in doped CoCr2O4. Further, frequency-dependent ac susceptibility (χ) fitted with different phenomenological models such as the Neel–Arrhenius, Vogel–Fulcher and power law confirm a spin-glass and/or cluster-glass behaviour in nanoparticles of CoCr2-xFexO4.

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Publication details

The article was received on 19 May 2017, accepted on 07 Jul 2017 and first published on 07 Jul 2017


Article type: Paper
DOI: 10.1039/C7DT01831B
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Cation Distribution Dependent Magnetic Properties in CoCr2-xFexO4 (x= 0.1 to 0.5): EXAFS, Mӧssbauer and Magnetic Measurements

    D. Kumar, A. Banerjee, A. Mahmoud and C. Rath, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT01831B

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