Ferromagnetism in ZnO Nanocrystals: Doping and Surface Chemistry
Ferromagnetism in ZnO Nanocrystals: Doping and Surface Chemistry
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DOI：
10.1021/jp909053f
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发表时间：
2010-01-28
影响因子：
3.7
通讯作者：
Mahamuni, Shailaja
中科院分区：
文献类型：
--
作者：
Inamdar, Darshana Y.;Lad, Amit D.;Mahamuni, Shailaja
在化学生长的ZnO纳米晶体中观察到室温铁磁有序。纳米晶体同时被两种不同的有机分子覆盖，诱导p型和n型缺陷。在300 K时，饱和磁化强度为0.008 emu/g。Mn ~（2+）离子在纳米晶中的取代位置的掺入在较低的掺杂水平下产生较高的饱和磁矩。在相同条件下制备的Mn ~（2+）和Co ~（2+）共掺杂ZnO纳米晶的饱和磁化强度增加。然而，饱和磁矩仍然低于通过相同方法制备的Co2+掺杂的ZnO纳米晶体。饱和磁化强度的增加总是与光致发光发射的淬灭。这些研究结果再次证实，磁性纳米晶体是一个缺陷引起的现象，可以通过选择的盖帽剂，以及过渡金属杂质的掺入控制。磁化强度作为温度[M（T）]曲线的函数进行了讨论，鉴于现有的报告，在这些铁磁纳米晶体的全球交换机制。
Room temperature ferromagnetic ordering is observed in chemically grown ZnO nanocrystals. Nanocrystals are simultaneously capped by two different organic molecules inducing p-type and n-type defects. A saturation magnetization of 0.008 emu/g is achieved at 300 K. Incorporation of Mn2+ ions at substitutional sites in nanocrystals gives rise higher saturation magnetic moment at lower doping level. ZnO nanocrystals codoped with Mn2+ and Co2+ and prepared under identical conditions revealed an increase in saturation magnetization. However, the saturation magnetic moment remains lower than that obtained for Co2+-doped ZnO nanocrystals prepared by the same method. An increase in saturation magnetization was invariably associated with quenching of photoluminescence emission. These findings reaffirm that magnetism in nanocrystals is a defect induced phenomenon that can be controlled by choice of capping agent as well as incorporation of the transition metal impurity. Magnetization as a function of temperature [M(T)] curve is discussed in view of available reports on the global exchange mechanism in these ferromagnetic nanocrystals.