Heat, Charge, and Spin: Thermal Spintronics in Ferromagnetic Films and Nanostructures

摘要：电荷在金属和半导体中的运动产生热量。电流中电子碰撞的这一基本结果意味着，电流在纳米尺寸的特征中快速流动的现代电子电路，由于高密度的热量而遭受损耗和其他挑战。如果信息可以以电子自旋的形式由角动量携带，那么大部分热量就可以避免。此外，最近的研究表明，将热应用于纳米磁系统可以为这种自旋电流提供长期寻找的来源，此外还可以应用于基于热、电荷和自旋流的能量收集。在这个项目中，首席研究员和他的研究小组对这些流动之间的相互作用进行了基础研究。关键技术是一种新的热隔离结构，可以精确测量磁性薄膜和纳米结构的微小温度变化。研究结果为热、电荷和自旋耦合现象提供了新的视角，并为设计和优化纳米电子学和能量收集的新设备奠定了必要的基础。技术摘要：纯自旋电流的产生是未来自旋电子纳米电子学模型的重要要求。然而，产生这种没有相关电荷的角动量流的可靠方法仍然难以捉摸。最近，一些研究小组报道，只要对铁磁材料施加热梯度，就能产生自旋电流。这种效应被称为自旋塞贝克效应，它引起了人们对铁磁系统中热、电荷和自旋相互作用的极大兴趣，也提高了基于磁性材料的新型热电器件的可能性。这种热电系统可以通过解耦热和电荷流来提供突破性的性能，这是热电材料的传统挑战之一。该项目扩展了首席研究员最近在薄膜金属铁磁体中的热电和热磁效应方面的工作。他的研究小组的测量是通过微机械热隔离平台实现的，该平台消除了由于高导热体基板的存在而引入的潜在混淆效应。这样可以精确测量热功率（传统的塞贝克效应），导热性和导电性，以及珀尔帖效应，以及各种不太为人所知的热电和热磁效应。所有这些测量都可以在单个样品上进行。这些新技术提供了控制纳米磁系统中热、电荷和自旋电流相互作用的物理探针，需要了解和优化它们在自旋电子学和能量产生方面的潜在用途。

Non-technical Abstract:The motion of charges through metals and semiconductors produces heat. This fundamental result of the collisions of electrons in electrical currents means that modern electronic circuits, where currents flow rapidly in features with nanometer dimensions, suffer losses and other challenges due to high densities of heat. If information could instead be carried by angular momentum in the form of the electron's spin, much of this heat can be avoided. Furthermore, recent work suggests that application of heat to nanomagnetic systems could provide a long-sought source for such spin currents, in addition to allowing possible applications in energy harvesting based on heat, charge, and spin flow. In this project, the principal investigator and his research team carry out fundamental studies of the interactions between these flows. The essential technique is a novel thermal isolation structure that allows accurate measurements of tiny temperature changes of magnetic thin films and nanostructures. The results allow a new view into the phenomena arising from the coupling of heat, charge, and spin, and form the essential foundations for designing and optimizing new devices for nanoelectronics and energy harvesting. Technical Abstract:The generation of pure spin currents is an important requirement for future spintronic nanoelectronics models. However, reliable methods to generate such a flow of angular momentum without associated charge remain elusive. Recently some groups have reported that a spin current can be produced simply by applying a thermal gradient to a ferromagnetic material. This effect, called the spin Seebeck effect, has generated tremendous interest in the interaction of heat, charge and spin in ferromagnetic systems and has also raised the possibility of new thermoelectric devices based on magnetic materials. Such thermoelectric systems could offer breakthrough performance by decoupling heat and charge flow, one of the traditional challenges in thermoelectric materials. This project extends the principal investigator's recent work on thermoelectric and thermomagnetic effects in thin film metallic ferromagnets. His research team's measurements are enabled by a micromachined thermal isolation platform that removes potentially confounding effects introduced by the presence of a highly thermally conductive bulk substrate. This allows accurate measurements of the thermopower (traditional Seebeck effect), thermal and electrical conductivity, and Peltier effects in addition to a variety of less widely known thermoelectric and thermomagnetic effects. All these measurements can be performed on a single sample. These novel techniques provide the probe of the physics governing the interaction of heat, charge and spin currents in nanomagnetic systems required to understand and optimize their potential use for spintronics and energy generation.