Magneto-transport in mutilayers and nanostructures with strong spin-orbit coupling

点击翻译按钮获取中文摘要

Many modern data storage and communications devices are made on a very small scale from magnetic materials. For example, modern computer hard drives and magnetic random access memory (MRAM) contain magnetic elements that are a few tens of nanometres in size. In such devices the direction of the magnetisation of the magnetic elements is used to store information. The methods currently used to control the direction of magnetisation involve using electrical current to generate a magnetic field locally or to switch the magnetisation using an effect called spin transfer torque . These techniques have disadvantages such as energy dissipation and limits on miniaturisation, due to the need to integrate the components which generate the field with other magnetic devices.A potential solution to these problems, which is being studied by the Experimental Condensed Matter Research Group at the University of Nottingham, would be to create devices in which the magnetic state is controlled by applying an electric field or a mechanical strain. Metallic alloys and multilayers which possess a strong relativistic effect called spin-orbit coupling are used. My proposal aims to study the properties of such materials and devices on a theoretical level. The direct collaboration with the experimental group at Nottingham will promote the applicability of the theoretical predictions, inspire new experiments and new theoretical investigations, and provide guidance in the design of the nanostructures. I will employ established theoretical models and techniques (such as the tight binding model and the Landauer Buttiker formalism) to calculate the magnetic and electrical properties of the devices. I will also use more advanced techniques (such as the non-equilibrium Green's function technique) to calculate the properties of the devices on ultra-fast timescales relevant to the speeds of information processing devices.I will complement these studies by inserting the results of the microscopic calculations into a macroscopic simulation and investigating the coupling of mechanical, electrical and magnetic degrees of freedom in nano-electro-mechanical systems (NEMS), which are devices such as nanoscale oscillating beams or cantilevers with potential applications as highly sensitive mass sensors and actuators. Such devices are also interesting for more fundamental studies of the overlap between quantum and classical physics.This proposal is motivated by both the academic and the commercial demand for developing a broader understanding of nanoscale devices made from metallic materials and multilayers possessing strong spin-orbit coupling and the search for new functionalities in such devices. The results of this work will lead the way to new non-volatile, electrically-manipulated memory devices.