Xray studies of the antiferromagnetic spin-density wave in CrV films

CrV 薄膜中反铁磁自旋密度波的 X 射线研究

• 批准号: EP/G06749X/2
• 负责人: Yeong-Ah Soh
• 金额: $ 13.56万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FG06749X%2F2
• 关键词: Xray; studies; antiferromagnetic; spin; density

New forms of order can develop in materials through phase transitions, which can change their properties drastically. We encounter examples of classical, thermal phase transitions in everyday life- we are very familiar with the freezing and melting of ice and condensing and boiling of water. Over the past few decades, physicists have become fascinated by order that emerges at absolute zero temperature, which is developed by varying quantum fluctuations instead of thermal fluctuations. We know far less about quantum phase transitions than classical phase transitions because it is more difficult to vary quantum fluctuations than to vary temperature in experiments. Therefore, few quantum phase transitions have been examined with the same level of precision as classical transitions. Even though quantum phase transitions occur at absolute zero temperature, they can have large effects on the properties of a material even at room temperature. The goal of our research is to study quantum phase transition in a common and familiar metal / chromium / rather than the more exotic rare earth intermetallics and transition metal oxides generally used for work on quantum phase transitions. Chromium develops an antiferromagnetic order, which is a hidden type of magnetic order and which can be altered and eventually destroyed by doping with vanadium (V)- the neighbor of chromium to the left on the periodic table. The order can also be altered by making the samples thin in film form. Our plan is to study this hidden magnetic order with x-rays since they have a wavelength smaller than the lengthscale of the hidden order and therefore provide us with a microscopic picture of the order. By studying samples with different V doping and thickness we will gain understanding on how quantum phase transitions depend on the dimensionality of the sample. In addition, materials with order can divide into the antiferromagnetic analogs of ferromagnetic domains, whose magnetizations point in different directions. Our goal is to understand the domains and the domain boundaries and eventually the properties of a single domain by using a focused x-ray beam smaller than the domain size to gain local information of the hidden order from domain to domain. Finally, when the dimension of a sample is small enough and comparable to a characteristic length scale that represents the property of the sample (electron wavelength or antiferromagnetic spin density wavelength), quantum size effects arise. Our goal is to study quantum size effects related to the development of the antiferromagnetic order. Developing a more detailed understanding of quantum phase transitions, antiferromagnetic domains, and quantum size effects in chromium will have a large scientific impact in statistical and solid state physics and perhaps lead to new devices that exploit these effects.

新的有序形式可以通过相变在材料中发展，这可以极大地改变材料的性质。我们在日常生活中遇到了经典的热相变的例子--我们非常熟悉冰的冻结和融化以及水的冷凝和沸腾。在过去的几十年里，物理学家们对绝对零度下出现的秩序很感兴趣，这种秩序是由不同的量子涨落而不是热涨落形成的。我们对量子相变的了解比经典相变要少得多，因为在实验中改变量子涨落比改变温度更难。因此，很少有像经典相变那样精确的量子相变被研究过。尽管量子相变发生在绝对零度，但即使在室温下，它们也可以对材料的性质产生很大影响。我们的研究目标是研究一种常见的常见金属/铬/的量子相变，而不是通常用于量子相变研究的稀有稀土金属间化合物和过渡金属氧化物。铬形成一种反铁磁性秩序，这是一种隐藏的磁性秩序，可以通过掺杂钒(V)来改变并最终摧毁这种秩序--钒(V)是铬在元素周期表上左边的邻居。也可以通过使样品以薄膜的形式变薄来改变顺序。我们的计划是用X射线研究这种隐藏的磁序，因为它们的波长比隐藏的有序的长度尺度小，因此为我们提供了一张这种有序的微观图像。通过研究不同V掺杂和不同厚度的样品，我们将了解量子相变是如何依赖于样品的维度的。此外，有序材料可分为铁磁区的反铁磁类似物，其磁化指向不同的方向。我们的目标是通过使用小于域尺寸的聚焦X射线束来获得域到域之间隐藏顺序的局部信息，从而了解域和域边界，并最终了解单个域的性质。最后，当样品的尺寸足够小，并且与代表样品性质的特征长度尺度(电子波长或反铁磁自旋密度波长)相当时，量子尺寸效应就产生了。我们的目标是研究与反铁磁有序发展相关的量子尺寸效应。发展对铬的量子相变、反铁磁区和量子尺寸效应的更详细的理解将在统计和固态物理中产生重大的科学影响，并可能导致利用这些效应的新设备。