摘要
用磁测量和Ｒａｍ ａｎ 光谱方法研究了尺寸和Ｃｏ２＋ 包附对αＦｅ２Ｏ３超微粉Ｍｏｒｉｎ 相变温度ＴＭ 的影响⒚随着样品尺寸的减小， ＴＭ 逐渐下降⒚Ｃｏ２＋ 包附可使１５０ｎｍ 的αＦｅ２Ｏ３超微粉的ＴＭ 从１９１Ｋ 降至７７Ｋ 以下⒚Ｒａｍ ａｎ 光谱测量显示αＦｅ２Ｏ３的光学声子频率随样品尺寸的减小而移向低频方向，暗示Ｆｅ３＋ 磁性离子与配位氧离子的键合减弱⒚此外还观察到声子谱因粒度减小和表面包附而发生了宽化⒚表明小粒子晶体中的原子间距不是单值，而是呈现某种分布⒚单离子各向异性能和磁性离子位能估算表明Ｆｅ３＋ 和Ｏ２－ 的距离因Ｃｏ２＋ 包附而增大，使单离子各向异性能减弱，导致Ｍｏｒｉｎ
The Morin transition temperature (T M ) of pure α Fe 2O 3 particles and α Fe 2O 3 coated with cobalt ions have been investigated by means of magnetic measurement and Raman spectroscopy. The results of the magnetic measurement showed that T M varies from 264 K to <77K with decrease in the size of the particles. The Raman spectra obtained indicates that the features were broadened and shifted down by 2～10 cm -1 with decrease of particle size, the surface coating by Co 2+ ions made these features broaden and shift down even more, which implies that the bonds of Fe O in the super fine particles with and without Co 2+ coating were weakened, and the bond length presents a certain distribution.
出处
《上海师范大学学报（自然科学版）》
1999年第1期51-56,共6页
Journal of Shanghai Normal University(Natural Sciences)
基金
上海市科学技术委员会回国留学人员资助项目
