Synthetic aluminum-substituted maghemites were characterized by total chemical analysis, powder X-ray diffraction (XRD), M?ssbauer 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 M?ssbauer 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.
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机译：合成铝取代的磁赤铁矿的特征是通过总化学分析，粉末X射线衍射（XRD），Msssbauer光谱法（ME）和振动样品磁强法（VSM）来表征。目的是确定随着Al浓度的变化，γ-Fe2-xAlxO3的结构，磁性和超精细性能。合成产品的XRD结果仅被索引为磁赤铁矿。增加Al替代Fe会降低平均晶体尺寸，并将所有衍射峰移至更高的o2θ角。根据方程a o = 0.8385-3.63 x 10-5 Al（R2 = 0.94），随着Al的增加，立方晶胞的a0尺寸减小。多数Msssbauer光谱由一个六重峰组成，但是在最高取代率142.5 mmol mol-1 Al时，在300 K处都获得了一个二重峰和六重峰。来自该副谱的所有超精细参数均与高自旋一致。 Fe3 +（0.2 a 0.7 mms-1），并暗示与双峰有关的强超顺磁性成分。六方体的超精细磁场随Al取代量的增加而降低[Bhf（T）= 49.751-0.1202Al; R2 = 0.94]，而线宽则线性增加。饱和磁化强度也随着同构取代的增加而降低。
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