Spin waves in ferromagnetic metallic wires

微线和纳米线就像小天线。在电磁场的存在下，比如无线电波，它们会产生一种纵向电流，这种电流可以被电子电路检测到。如果这个小金属天线也是磁性的，导线中的感应电流可以被外部磁场强烈地改变。这种效应被称为磁阻抗，可以用来探测非常小的磁场。这对于地质勘探、金属物体探测或生物医学成像等应用非常有用。我们也可以制造一种人造材料，由一层薄薄的小磁性纳米线制成，就像一片小圆柱形磁铁的森林。这种所谓的磁晶体对无线技术中使用的无线电波很敏感。因此，磁振晶体可以在诸如手机等应用中用于检测和处理无线信号。在这项发现基金中提出的研究旨在对这些磁性微线和纳米线如何对电磁场作出反应有一个基本的了解。这些磁线的特别之处在于，它们的磁性是由微小的磁体（称为自旋）在特定频率下像小波一样被激发出来的。这些自旋波与要检测的电磁信号和电线中的电流相互作用。我们研究如何利用这种相互作用来检测、传输或转换信号，这在简单金属中是不可能的。申请的经费主要用于资助两名博士生和五名本科生的暑期研究项目。这项工作的可能成果包括新的微波材料或无线技术的新设计可能性和更好的磁传感器。

Micro- and nanowires are like small antennas. In presences of an electromagnetic field, like radio waves, they develop a longitudinal electrical current that can be detected by an electronic circuit. If this small metallic antenna is also magnetic, the induced electrical current in the wire can be strongly modified by an external magnetic field. This effect, called magnetoimpedance, can be used to detect very small magnetic field. This is useful for applications such as geo-prospection, detection of metallic objects or biomedical imaging. We can also build an artificial material, made out of a thin layer of small magnetic nanowires, like a forest of small cylindrical magnets. This so-called magnonic crystal is sensitive to the radio waves used in wireless technologies. Therefore, the magnonic crystal can be useful in applications, such as cell phones, to detect and process wireless signals. The research proposed in this Discovery Grant aims to develop a fundamental understanding of how these magnetic micro- and nanowires respond to electromagnetic fields. What makes these magnetic wires special is that the microscopic magnets, called spins, responsible for their magnetic properties can be excited like small waves, at specific frequencies. These spin waves interact with the electromagnetic signal to be detected and with the electrical currents in the wires. We investigate how this interaction can be exploited to detect, transport or transform signals in ways that are not possible in simple metals. The funds requested are essentially for the financial support of the research of two PhD students and five undergraduate students for summer research projects. Possible outcomes of the work include new microwave materials or new design possibilities for wireless technologies and better magnetic sensors.