Microwave properties of nanostructured magnetic materials

材料的电磁特性工程是许多现代技术领域的一个重要挑战。我们的研究项目旨在设计、开发和表征具有可定制EM特性的人工纳米结构材料。重点是频谱的微波范围。电磁响应受阻抗和色散关系的支配，一般可以通过调节材料的有效磁导率、介电常数和电导率来控制。通过在介质或半导体基体中结合金属和铁磁性纳米内含物，我们可以利用各种电荷和自旋输运现象，以及自旋和电荷密度波，来实现自然界中没有的磁和介电响应。这可能会导致第一个场可调谐左手超材料的演示。本课题主要研究电镀在纳米多孔氧化铝膜上的铁磁纳米线阵列。所要求的资金主要用于学生的经济支持。具体目标是：(1)证明在相同微波频率范围内具有显著磁和介电色散的人造材料的存在，并由外部磁场控制；(2)了解限制此类材料实际应用的耗散机制，并探索最小化和补偿它们的不同途径；(3)建立有效电磁波在材料中的传播条件。除了磁性纳米线系统，研究的其他材料包括嵌入III-V型半导体薄膜、多铁薄膜和碳纳米管薄膜的铁磁性纳米团簇。工作成果包括：新的可定制的低损耗材料和微波电路（无线技术）的新设计可能性，以及具有室温以上磁性功能的技术相关半导体，为高速电子和光电子之间提供功能桥梁。

The engineering of electromagnetic (EM) properties in materials is an important challenge in many areas of modern technology. Our research program aims to design, develop and characterize artificially nanostructured materials, with tailorable EM properties. The focus is on the microwave range of the spectrum. The EM response is governed by the impedance and dispersion relations and can be generally controlled by adjusting of the effective permeability, permittivity and conductivity of materials. By combining metallic and ferromagnetic nanoinclusions in a dielectric or a semiconducting matrix, we can exploit various charge and spin transport phenomena, along with spin and charge density waves, to achieve magnetic and dielectric responses not found in nature. This could lead to the possible demonstration of the first field-tunable left-handed metamaterials. This proposal is mainly concerned with arrays of ferromagnetic nanowires electroplated in nanoporous alumina membranes. The funds requested are essentially for the financial support of students. The specific objectives are: (1) to demonstrate the existence of artificial materials with significant magnetic and dielectric dispersions over the same microwave frequency range and controllable by an external magnetic field, (2) to understand the dissipation mechanisms limiting practical applications in such materials and to explore different avenues to minimize and compensate them, (3) to establish the conditions for effective magnetic wave propagation in the materials. In addition to magnetic nanowire systems, other materials studied include ferromagnetic nanoclusters embedded in III-V semiconductor epilayers, multiferroic thin films and films of carbon nanotubes. Outcomes of the work include: new tailorable low-loss materials and new design possibilities for microwave circuits (wireless technologies), and technologically relevant semiconductors with magnetic functionalities above room temperature, providing functional bridge between high speed electronic and optoelectronics.