Structural and magnetic characterization of maghemites prepared from Al-substituted magnetites

Revista Brasileira de Ciência do Solo

Marcelo Augusto Batista²  Antonio Carlos Saraiva Da Costa¹  Jerry Marshal Bigham¹  Andrea Paesano Junior¹  Graciele Berndt¹  Tadeu Takeyoshi Inoue²  Adriele Galeti Nonaka¹ 

[1] ,State University of Maringá Departament of Agronomy Maringá PR ,Brazil

关键词: isomorphous substitution;    hyperfine parameters;    spinel;    ferromagnetic;    substituição isomórfica;    parâmetros hiperfinos;    espinélio;    ferrimagnético;   

DOI  :  10.1590/S0100-06832013000600013

来源: SciELO

【 摘 要 】

Synthetic aluminum-substituted maghemites were characterized by total chemical analysis, powder X-ray diffraction (XRD), Mössbauer spectroscopy (ME), and vibrating sample magnetometry (VSM). The aim was to determine the structural, magnetic, and hyperfine properties of γ-Fe2-xAl xO3 as the Al concentration is varied. The XRD results of the synthetic products were indexed exclusively as maghemite. Increasing Al for Fe substitution decreased the mean crystalline dimension and shifted all diffraction peaks to higher º2θ angles. The a0 dimension of the cubic unit cell decreased with increasing Al according to the equation a o = 0.8385 - 3.63 x 10-5 Al (R²= 0.94). Most Mössbauer spectra were composed of one sextet, but at the highest substitution rate of 142.5 mmol mol-1 Al, both a doublet and sextet were obtained at 300 K. All hyperfine parameters from the sub-spectra were consistent with high-spin Fe3+ (0.2 a 0.7 mms-1) and suggested a strong superparamagnetic component associated with the doublet. The magnetic hyperfine field of the sextets decreased with the amount of Al-substitution [Bhf (T) = 49.751 - 0.1202Al; R² = 0.94] while the linewidth increased linearly. The saturation magnetization also decreased with increasing isomorphous substitution.

【 授权许可】

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