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.

材料中可以通过相变形成新的有序形式，这可以极大地改变它们的特性。我们在日常生活中遇到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，物理学家对绝对零温度下出现的秩序着迷，这种秩序是由不同的量子涨落而不是热涨落产生的。我们对量子相变的了解远少于经典相变，因为在实验中改变量子涨落比改变温度更困难。因此，很少有量子相变能够以与经典相变相同的精度进行检查。尽管量子相变发生在绝对零温度下，但即使在室温下，它们也会对材料的性能产生很大影响。我们研究的目标是研究常见且熟悉的金属/铬/中的量子相变，而不是通常用于量子相变工作的更奇特的稀土金属间化合物和过渡金属氧化物。铬形成一种反铁磁序，这是一种隐藏类型的磁序，可以通过掺杂钒（V）（元素周期表中铬的左边邻居）来改变并最终破坏它。也可以通过将样品制成薄膜形式来改变顺序。我们的计划是用 X 射线研究这种隐藏的磁序，因为它们的波长小于隐藏序的长度尺度，因此为我们提供了磁序的微观图像。通过研究具有不同 V 掺杂和厚度的样品，我们将了解量子相变如何取决于样品的维度。此外，有序材料可以分为铁磁畴的反铁磁类似物，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 射线束来了解域和域边界，并最终了解单个域的属性，以获得域与域之间隐藏顺序的局部信息。最后，当样品的尺寸足够小并且与代表样品特性的特征长度尺度（电子波长或反铁磁自旋密度波长）相当时，就会出现量子尺寸效应。我们的目标是研究与反铁磁序发展相关的量子尺寸效应。对铬中的量子相变、反铁磁畴和量子尺寸效应进行更详细的了解将对统计和固态物理学产生巨大的科学影响，并可能带来利用这些效应的新设备。