Study of the Effect of Cu²⁺ in the Lattice Dynamics of Doped Magnetites Obtained by the Hydrothermal Synthesis Method

A. A. Velásquez, J. P. Urquijo

Grupo de Electromagnetismo Aplicado, Universidad EAFIT, Medellín, Colombia.
Grupo de Estado Sólido, Universidad de Antio- quia, Medellín, Colombia..

DOI: 10.4236/sar.2013.12002                

Abstract

In this work, the effect of Cu²⁺ on the structural and magnetic properties of samples of magnetite is addressed. Samples
of magnetite, both pure and Cu²⁺ doped, Fe_3-xCu_xO₄, with x = 0, 5, 10 and 20 atm.% were synthesized hydrothermally. The two-lattice method was employed to measure the Mossbauer recoilless fraction of magnetite relative to hematite (f_mag/f_hem)
of the samples, looking for evidence of substitution of Fe²⁺ by Cu²⁺. The relative recoilless fraction measurements were performed by taking room temperature Mossbauer spectra of mixtures of each sample with analytical grade hematite. The Mossbauer measurements were complemented with Atomic Absorption Spectroscopy (AAS) and Energy Dispersive X-ray Spectroscopy (EDS). The analyses by AAS and EDS showed that the copper concentration in the final products
increases with increasing the content of Cu²⁺ in the starting solutions. The Mossbauer analyses showed a linear decrease trend of the relative Mossbauer recoilless fraction with increasing concentration of Cu²⁺in the samples, as well as a reduction in the hyperfine magnetic field, which was more significant in the octahedral sites than tetrahedral sites. The broadening of the Mossbauer spectral lines was more significant for the octahedral sub spectrum than for the tetrahedral sub spectrum. Our study points that Cu²⁺ occupies preferentially the octahedral sites, where it substitutes Fe²⁺ species, generating broadening in the lines of the octahedral sub spectrum and a reduction in the probability of having nuclear resonant absorption of Mossbauer gamma rays in the samples.

Keywords

Doped Magnetites; Mössbauer Recoilless Fraction; Divalent Copper

Conflicts of Interest

The authors declare no conflicts of interest.

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