(中山大學(xué)物理系，廣州510275)
摘 要: 采用惰性氣體保護(hù)蒸發(fā)凝聚技術(shù)制備出粒徑為4~15nm的稀土金屬Gd微粉(nm-Gd)。經(jīng)振動樣品磁強(qiáng)計測試，表明nm-Gd微粉在某一特征粒徑dc時磁化率χ取得最小值。利用小角X射線散射方法分析了nm-Gd微粉的三維生長分形特征，表明nm-Gd微粒聚集體系呈質(zhì)量分形，制備氣壓越小則分維系數(shù)Df越小。微粒生長模型是擴(kuò)散限制聚集(DLA)與擴(kuò)散限制團(tuán)聚聚集(DLCA)模型共存，相應(yīng)這兩個模型階段的分維系數(shù)Df存在一特征粒徑df。根據(jù)納米微粒理論對nm-Gd微粉體系的量子尺寸效應(yīng)的特征尺dq進(jìn)行了估算，并就三種特征粒徑dc、df和dq進(jìn)行了分析和比較。
關(guān)鍵字: 稀土金屬 納米材料 磁性 生長分形
GROWTH FRACTAL CHARACTERISTICS OF
NANOMETER GADOLINIUM POWDER
（Department ofPhysics, Zhongshan University, Guangzhou 510275）
Abstract:Nanometer gadolinium powders (nm-Gd) sized 4~15 nm have been prepared by means of condensation of evaporating Gd atoms in the atmosphere of inert gas argon. The magnetic susceptibility of nm-Gd powders, measured by vibrating samples magnetometer, demonstrates a minimum when the size of nm-Gd powder approaches a special value dc. The analysis, based on the measurement of small angle X-rays scattering, shows that the as-prepared nm-Gd powders have a characteristic of mass fractal growth, and that a lower pressure of inert gas results in a small fractal dimensionDf. There are two stages corresponding to DLA (Diffusion Limited Aggregation) and DLCA(Diffusion Limited Cluster Aggregation) models in the growing process of nm-Gd powders. There exists a special sizedfof nm-Gd powder about fractal dimension between the two stages mentioned above also. According to the theory of nanometer materials, a calculation evaluating the critical sizedqof quantum-size effect of metal Gd has been carried out in order to clarify the influence of three special sizesdf,dqanddcon the magnetic susceptibility of nm-Gd powders.
Key words: rare-earth metal nanometer materials magnetic property growth fractal
