Quantum Materials Studied with muSR and beta-NMR

使用 muSR 和 β-NMR 研究量子材料

• 批准号: RGPIN-2019-05105
• 负责人: Kiefl, Robert
• 金额: $ 2.04万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715343
• 关键词: Quantum; Materials; Studied; muSR; beta

All electronic, magnetic and structural properties are altered near a boundary between two materials. Consequently a thin film or the near surface region of a crystal has properties that in general are different than in the bulk. In some cases it may be possible to control such properties with an electric or magnetic field. Devices using such effects have had a dramatic impact on magnetic storage of information. A second theme for my research is coherent properties of quantum materials. The low temperature properties of materials are particularly interesting since that is where we expect effects due to coherence to be largest. Materials which exhibit interesting quantum phenomena at low temperatures (e.g. superconductivity) are sometimes called “quantum materials”. Our objectives are to explore and eventually control the electronic/magnetic properties near the interfaces and surfaces of quantum materials. This will help create a more unified picture of how electrons and magnetic ions organize themselves into coherent states of matter at low temperatures, how these properties change near interfaces and how they can be controlled with external fields. The potential impact comes from the expectation that future devices will increasingly utilize the properties of interfaces and thin films of quantum materials. We will use powerful new methods to explore local magnetic properties as a function of depth on a nanometer length scale. One of them, called low energy beta-detected nuclear magnetic resonance (beta-NMR), has been developed in Canada. A closely related method, low energy muon spin rotation/relaxation (muSR) , is possible at the Paul Scherrer Institute (PSI) in Switzerland. The two methods have similar principles but provide complementary information. The magnetic moment of the muon (or radioactive nucleus) acts as a probe of the local magnetic/electronic environment. The two methods are closely related to nuclear magnetic resonance imaging commonly known as MRI. All forms of nuclear magnetic resonance involve generation of a non-equilibrium spin polarization followed by observation of the time dependent polarization. muSR and beta-NMR are distinct in that the polarization is detected through the anisotropic decay properties of the muon or nucleus. Consequently a signal can be observed in structures that are 10 orders of magnitude smaller than is required in conventional NMR or MRI. In particular these methods allow one to probe the internal magnetic and electronic properties in very thin films which are a million times thinner than of a human hair.

在两种材料的边界附近，所有的电子、磁性和结构特性都会发生变化。因此，薄膜或晶体的近表面区域具有通常不同于体中的性质。 在某些情况下，可以用电场或磁场来控制这些性质。利用这种效应的设备对信息的磁存储产生了巨大的影响。我研究的第二个主题是量子材料的相干特性。材料的低温特性特别令人感兴趣，因为这是我们预期相干性效应最大的地方。在低温下表现出有趣的量子现象（例如超导性）的材料有时被称为“量子材料”。我们的目标是探索并最终控制量子材料界面和表面附近的电子/磁性。这将有助于创建一个更统一的图像，说明电子和磁性离子如何在低温下组织成物质的相干态，这些特性如何在界面附近变化，以及如何用外部场控制它们。潜在的影响来自于对未来设备将越来越多地利用量子材料的界面和薄膜特性的期望。 我们将使用强大的新方法来探索局部磁性作为纳米长度尺度上的深度的函数。其中之一，称为低能β-探测核磁共振（β-NMR），已在加拿大开发。一个密切相关的方法，低能μ子自旋旋转/弛豫（muSR），是可能的保罗谢勒研究所（PSI）在瑞士。这两种方法具有相似的原理，但提供了互补的信息。μ子（或放射性核）的磁矩充当局部磁/电子环境的探针。 这两种方法与通常称为MRI的核磁共振成像密切相关。所有形式的核磁共振都涉及非平衡自旋极化的产生，然后观察随时间变化的极化。μ SR和β-NMR的不同之处在于，通过μ子或原子核的各向异性衰减特性来检测极化。因此，可以在比常规NMR或MRI中所需的小10个数量级的结构中观察到信号。 特别是，这些方法允许人们探测比人类头发薄一百万倍的非常薄的薄膜中的内部磁性和电子特性。