CdS:Mn/SiO_2复合纳米颗粒的反常的磁学特性(英文)

Anomalous magnetic behaviour of CdS:Mn/SiO_2 nanocomposites

采用反胶束法,合成了硅土包裹的Mn^(2+)掺杂的CdS纳米颗粒.利用高分辨透射电镜(HRTEM)和电子自旋共振谱(EPR)对这些纳米颗粒的结构进行了表征.利用超导量子干涉磁力计(SQUID)测量了这些纳米颗粒在低温下的磁学特性.研究结果表明:扩散在硅土基质中的CdS:Mn纳米颗粒的磁滞回线相对于磁场轴有明显的偏移,而有致密包裹层SiO_2的CdS:Mn纳米颗粒却使磁滞回线的偏移消失,对于磁性纳米颗粒在磁化过程中出现的这一奇特的现象进行了合理的解释.

Silica-overcoated CdS nanocrystals doped with Mn^2＋ ions were synthesized by a reverse-micelle method. Structural characterization of the nanoparticles was carried out with high resolution transmission electron microscopy （HRTEM） and the electron paramagnetic resonance （EPR） and their magnetic properties were measured by superconducting quantum interference device （SQUID） magnetometry at lower temperature. The result of measurement indicates that as-synthesized nanocrystals dispersed in a silica matrix exhibit obvious shift of the hysteresis loop toward the field direction, however, the nanocrystals coated with compact SiO2 shell display symmetric hysteresis loop. The reasonable explanations are presented for the unusual phenomenon during magnetization process.