Magnetism in reduced dimensions: Nanoparticles, thin films and quantum spin systems

降维磁性：纳米粒子、薄膜和量子自旋系统

• 批准号: 311888-2008
• 负责人: vanLierop, Johan
• 金额: $ 1.91万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2012
• 资助国家: 加拿大
• 起止时间: 2012-01-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=497925
• 关键词: Magnetism; reduced; dimensions; Nanoparticles; thin

Nanomagnetism in nanoparticles, thin films, and quantum spin systems: Metals-based crystallites with sub-100 nm sizes, called nanoparticles, exhibit a wide range of physical properties that are strikingly different from their bulk counterparts. Many novel properties arise from the large fraction of atoms that reside on the surface and the finite number of atoms in each nanoparticle core. Our research program is dedicated to answering the fundamental question: what overall effect does the surface have on the nanoparticle magnetism. The magnetic frustration effects from the surface and core magnetism dichotomy in a nanoparticle can be "peeled" away onto a 2D surface. A thin film that is a ferromagnetic layer interfaced to an antiferromagnetic layer is an ideal example. Just like a nanoparticle, such a film exhibits the exchange bias effect. Exchange bias is the result of magnetic moments at the interface which are "locked-in". The physical origins of this "locking" are currently unknown. With a unique combination of nanoscale structural characterization, and a comprehensive description of the nanomagnetism from atomic to the bulk length scales, we intend to enable new insights into the physics of the "locking". A further reduction in the degrees of freedom is possible in certain structures where interactions are possible in only one crystallographic direction. A 1D quantum spin system is then created, an example of which are Haldane gap materials. These materials exhibit novel magnetism. Quantum spin systems present a unique theoretical description whose robustness still requires rigorous experimental tests. Our research group's significant experience measuring and modeling static and dynamic magnetism will provide unique insights into the physics of these materials. There is an unmistakable, pressing need for knowledge in the above research areas. First, the next generation of magnetic media hinges on shrinking device sizes where successful implementation depends on understanding the nanomagnetism. Second, new medical technologies based on nanoparticle drug delivery require a comprehensive understanding of the magnetism of single and collections of nanoparticles.

纳米颗粒，薄膜和量子自旋系统中的纳米磁学：基于金属的结晶石，具有近100 nm尺寸的纳米颗粒，称为纳米颗粒，具有与大量对应物的巨大物理特性。 许多新颖的特性来自驻留在表面上的大量原子，每个纳米颗粒核中的原子数量有限。 我们的研究计划致力于回答以下基本问题：表面对纳米颗粒磁性的总体影响是什么。 纳米颗粒中表面和核心磁性二分法的磁挫败感可以“剥离”到2D表面上。 一个连接到抗铁磁层的铁磁层的薄膜是一个理想的例子。 就像纳米颗粒一样，这种膜也表现出交换偏置效果。 交换偏差是界面处的磁矩的结果，该磁矩是“锁定”的。 目前未知该“锁定”的物理起源。通过纳米级结构表征的独特组合，以及对从原子到批量尺度的纳米磁性的全面描述，我们打算使对“锁定”物理学的新见解。 在仅在一个晶体学方向上进行相互作用的某些结构中，可以进一步降低自由度。 然后创建了一个1D量子自旋系统，其示例是Haldane Gap材料。 这些材料表现出新颖的磁性。量子自旋系统提出了独特的理论描述，其鲁棒性仍然需要严格的实验测试。 我们的研究小组的衡量和建模静态和动态磁性的丰富经验将为这些材料的物理学提供独特的见解。 在上述研究领域中，有一个明确的知识需求。 首先，下一代磁媒体取决于缩小设备大小的缩小，成功实施取决于理解纳米磁性。 其次，基于纳米粒子药物输送的新医疗技术需要全面了解纳米颗粒的磁性和集合的磁性。