摘要
本文首次用Raman光谱法研究了粒子尺寸和Co2 +包附对α-Fe2 O3纳米粒子Morin相变温度TM的影响机制。测量结果显示纳米粒子α -Fe2 O3的振动模相对大块样品发生了红移和宽化 ,粒子愈小红移和宽化愈显著。表明表面Fe3+离子与配位氧离子的键距增大 ,键长呈从体相Fe-O键长过渡到表面Fe -O键长的某种分布。这种小尺寸引起的键长改变导致α -Fe2 O3粒子的单离子各向异性能减小 ,因此降低了样品的TM。分析显示Co2 +包附导致α -Fe2 O3粒子TM 的大幅下降可能是由单离子各向异性的减小和Co2
The influence of the size and surface coating on the Morin transition (T M) of α-Fe 2O 3 nanoparticles has been investigated by magnetic measurement and Raman spectroscopy The results of the magnetic measurement show that T M varies from 264 K to 92 K with decrease in the size of the particles Whereas Co 2+ coating made T M of the particles down even more The Raman spectra obtained indicates that the bands were broadened and shifted down by ca 2-14 cm -1 with decrease of the particle size and Co 2+ coating, which imply that the Fe-O bonds of the particles were weakened It may give rise to the decrease of the single ion anisotropy of α-Fe 2O 3 particles, resulting in the decrease in T M The largest decrease in T M of Co 2+ coating α-Fe 2O 3 particles is probably caused by the co-action of the decrease in the single ion anisotropy and magnetic dipole anisotropy
出处
《光散射学报》
2001年第4期220-225,共6页
The Journal of Light Scattering
