非磁性元素掺杂稀磁半导体铁磁性机理研究的新方法

要研究非磁性元素掺杂DMS材料的铁磁性机理，需澄清"局域磁矩"来源和"局域磁矩间耦合的媒介"。已有理论基于3d过渡金属元素掺杂DMS材料，不适用于非磁性元素掺杂DMS体系。电子磁圆二色谱(EMCD)技术，结合传统电子能量损失近边精细结构（ELNES），提供了该问题研究的新途径。本项目利用EMCD方法，在透射电镜下进行高空间分辨率的，元素分辨的磁性测量。探测到EMCD信号的元素对局域磁矩有贡献，可推导出DMS材料的"局域磁矩"来源；进行不同元素的ELNES和价电子能量损失谱（VEELS）实验，结合材料电子结构的第一性原理计算，研究DMS材料费米面附近的电子态密度和元素的配位及成键情况，可探测"局域磁矩间耦合的媒介"。本项目侧重于材料表征，满足DMS材料对表征方法的高要求。对于深入理解非磁性元素掺杂DMS材料的电子结构，局域磁矩来源及相互作用，澄清铁磁性机理具有重要意义。

To investigate the origination of ferromagnetism in non-magnetic elements doped diluted magnetic semiconductors (DMS), the localized magnetic moments and the coupling media between them have to be clarified. The existing ferromagnetic theories are based on 3d-transition metal doped DMS, cannot be applied to the non-magnetic elements doped DMS system. The developed electron magnetic chiral dichroism (EMCD)method, combining with the conventional energy-loss near edge structure (ELNES),provide the new route to study the ferromagnetism machanism of non-magnetic element doped DMS system. In this project, the selective observation on magnetic polarization of each element in non-magnetic elements doped DMS are performed by means of EMCD technique.The EMCD signal can be measured for the element producing spin polarization.The origination of local magnetic moments in non-magnetic elements doped DMS can thus be deduced. By using ELNES and valence electron energy loss spectroscopy (VEELS), the density of states near the Fermi level are investigated. The first principle calculations are used to simulate the ELNES and VEELS, which provide the clear image of the electronic structure of non-magnetic elements doped DMS. The local coordination environment of each elements can be deducted and thus the coupling media between local magnetic moments can be clarifed. The studies focus on the characterization of DMS materials and are based on transmission electron microscopy, owing the super-higher spatial resolution. The project is helpful for the understanding of the ferromagnetism mechanism of non-magnetic elements doped DMS system.