Magneto-optic studies of ZnO based magnets

ZnO基磁体的磁光研究

基本信息

批准号：
EP/D070406/1
负责人：
Gillian Gehring
金额：
$ 39.26万
依托单位：
University of Sheffield
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FD070406%2F1
关键词：
Magneto optic studies ZnO based

项目摘要

Zinc oxide is a transparent crystal that does not conduct electricity. It is not magnetic.Recently it has been found that if one in 50 of the Zn atoms is replaced by a manganese or cobalt atom and the material has additional defects that add electrons that cause it to conduct electricity then it becomes magnetic at room temperature. Magnetism comes from the electrons that are associated with the magnetic atoms.Of course there are other room temperature magnets such as iron but they are metals. A magnetic semiconductor is something really new and exciting. Such a material has many applications in new devices that combine the memory capabilities of a magnet with semiconductor electronics. The magnetism arises from the widely separated magnetic atoms that line up to make one big magnet. Some of the electrons are stuck around the defects and some are free to move. An electron that is stuck near a defect may only be sensitive to the magnetism of one of the localised magnetic atoms. The electric current comes from those that are free to move and it is these electrons that will move past many magnetic atoms and cause the magnetic moments on the individual magnetic ions to line up. This happens because all electrons actually have their own little magnetic moment.Sheffield WORLD LEADING experiments show that the band edge transitions of ZnO films have a magnetic signature when doped with any one of vanadium, titanium, cobalt or manganese. This is the first clear and unambiguous demonstration that the conduction electrons of ZnO are magnetic and hence that that ZnO is a dilute magnetic semiconductor. This proposal is to use the apparatus and expertise in Sheffield to use magneto-optic spectra, absorption spectra, Hall effect measurement of the free carrier density and SQUID magnetisation measurements to establish the magnitude of the conduction electron polarisation and the nature of the ferromagnetism.This has enormous implications because it shows that the bulk magnetism observed at room temperature is really connected with the ZnO. It also opens the way for the exploitation of the storage capacity associated with the magnetism to be integrated with ultra violet light, that has a very small wavelength, this will allow a much higher density of information to be recorded and read than is currently possible with the standard lasers that use red light. We have made the first groundbreaking experiments in this area. What is needed now is to build on the understanding that we have developed. We want to extend the experimental technique to include the absorption of light as well as the response of the light to the magnetism. We want to use the method that we have developed to make the detailed studies of the behaviour of the doped ZnO films with different concentrations of dopants, different thicknesses and different temperatures. We need the grant to start on 1 April so that we can employ the research fellow who has built the apparatus that we use and also taken all the measurements so far. If there is a delay and we lose this continuity we shall lose our world leading position...

氧化锌是一种透明晶体，不导电。它不具有磁性。最近发现，如果 50 个 Zn 原子中的一个被锰或钴原子取代，并且该材料具有额外的缺陷，增加了导致其导电的电子，那么它在室温下就会变成磁性的。磁性来自与磁性原子相关的电子。当然还有其他室温磁铁，例如铁，但它们是金属。磁性半导体是一种非常新颖且令人兴奋的东西。这种材料在将磁体的记忆能力与半导体电子器件相结合的新设备中具有许多应用。磁性来自于相距较远的磁性原子，这些原子排列在一起形成一个大磁铁。一些电子被困在缺陷周围，一些电子可以自由移动。卡在缺陷附近的电子可能只对局部磁性原子之一的磁性敏感。电流来自那些可以自由移动的电子，正是这些电子将移动经过许多磁性原子并导致单个磁性离子上的磁矩排列起来。发生这种情况是因为所有电子实际上都有自己的小磁矩。谢菲尔德世界领先的实验表明，当掺杂钒、钛、钴或锰中的任何一种时，ZnO 薄膜的带边跃迁具有磁性特征。这是第一次清晰明确地证明 ZnO 的传导电子是磁性的，因此 ZnO 是一种稀磁性半导体。该提案是利用谢菲尔德的设备和专业知识，利用磁光光谱、吸收光谱、自由载流子密度的霍尔效应测量和 SQUID 磁化强度测量来确定传导电子极化的大小和铁磁性的性质。具有巨大的意义，因为它表明在室温下观察到的体磁性确实与 ZnO 有关。它还为利用与磁性相关的存储容量与波长非常小的紫外线集成开辟了道路，这将允许记录和读取比目前可能更高的信息密度。使用红光的标准激光器。我们在这个领域做了第一个突破性的实验。现在需要的是建立在我们已经形成的理解的基础上。我们希望将实验技术扩展到包括光的吸收以及光对磁性的响应。我们希望利用我们开发的方法对不同掺杂浓度、不同厚度和不同温度的掺杂ZnO薄膜的行为进行详细研究。我们需要从 4 月 1 日开始拨款，这样我们就可以聘请建造我们使用的设备并进行迄今为止所有测量的研究员。如果出现延误，我们就失去了这种连续性，我们将失去我们的世界领先地位......