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Structural, magnetic, and Mossbauer studies of magnetite and nickel-copper and nickel-zinc ferrites
Authors: Ounacer, M.; Rabi, B; Agouriane, E.; Essoumhi, A.; Sajieddine, M.; Costa, BFO
Ref.: Inorg. Chem. Commun. 158(2), 111650 (2023)
Abstract: This work aims to investigate the magnetite obtained by coprecipitation, as well as the mixed ferrites of nickel-copper and nickel-zinc. The as-prepared samples were then annealed at a temperature (T-an) of 1000 degrees C. The as-prepared magnetite shows a polycrystalline spinel structure having an average of crystallite size (D-XRD) of 8 nm, while other as-prepared mixed ferrites are structurally amorphous. Annealing at T-an has resulted in an improvement in the crystallinity of both nickel-copper ferrites (NCF, D-XRD = 92 nm) and nickel-zinc ferrites (NZF, D-XRD = 83 nm), both of which exhibit a cubic spinel structure. The thermal treatment in air atmosphere has also led to the oxidation of magnetite into hematite. Morphological observations suggest that the magnetite nanoparticles are nearly spherical, whereas the NCF and NZF particles indicate irregular shapes, which tend to aggregate. Magnetic curves reveal that the NCF exhibits a blocking temperature (T-B) close to room temperature, while the NZF sample displays the lowest T-B at 45 K. Additionally, the NZF exhibits a higher M-s value of 80.4 emu/g and displays a narrow hysteresis loop, which makes it suitable for applications in hyperthermia. The Fe-57 Mossbauer study on magnetite and NZF indicates broadening spectra, which is due to superparamagnetic relaxation, thus the fit their spectra was established with hyperfine field distribution component. Regarding the NCF Mossbauer spectrum was adjusted by superimposing two sextets reflecting the presence of Fe3+ at the A and B sites of spinel. The hyperfine parameters, including the isomer shift, and hyperfine field, have been systematically reported in the present study.
