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

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.

Who will benefit from this research: My proposal offers insight into the fundamental physical processes in nanoscale magnetism and is broadly in line with the EPSRC theme of Nanosciences through engineering to application . In the immediate term, the project will be of direct benefit to the experimental groups in Nottingham, Hitachi Cambridge Laboratory, and in other laboratories studying magnetisation and spintronics in metallic nanoscale devices. In the longer term, the UK companies active in the area of magneto-electronics will benefit from the proposed research. The local schools and societies will benefit through a programme for public engagement including outreach visits and lectures at the School of Physics and Astronomy in Nottingham. The general public will benefit indirectly through the potential improvement in information and communication technologies. How will they benefit from this research: The economic competitiveness and cultural development of a modern society relies on efficient ways of tracking, exchanging, and storing the relevant information. The development of fast, energy efficient nanoscale devices for data storage and processing is of critical importance to the continuing innovation in information and communications technologies. The proposed project addresses these challenges directly by aiming to make the spin-orbit phenomena (control of magnetisation direction by electric fields or strain) available at room temperature and to pave the way to a non-volatile electrically manipulated memory device, highly accurate sensors and actuators. The realistic timescales for the application of the theoretical results in functional devices are of the order of months due to the direct collaboration with the experimental groups. In case of successful development on the academic level the fabrication of a commercially exploitable device takes 2-5 years and is facilitated by the presence of the industrial partner. The staff (myself) working on the project will acquire a wide range of skills applicable in an academic or industrial employment, e.g., advanced usage of the Comsol engineering and scientific software package. What will be done to ensure the opportunity to benefit from this research: This theoretical research programme will be carried out in collaboration with the experimental groups in order to have a direct impact on the design and functionality of new devices in data storage and processing. The main strand of the research is complemented with the macroscopic simulations of magnetic nanodevices which represents a bridge between the fundamental research and the engineering applications. As a research fellow I will collaborate closely with the experimental research group at the host organisation and will visit the Hitachi Cambridge Laboratory on regular basis. I will have discussions with the staff on the design and fabrication of the relevant materials and devices. I will seek to publish the results of the work in the leading physics and general science journals. I will also present the work at the key international conferences on magnetism and spintronics (e.g. International Conference on Magnetism, Spintech and MMM-Intermag). The proposed collaboration with Hitachi Cambridge Laboratory (Hitachi Europe Ltd.) builds upon a previous very successful collaboration, also involving the host organisation, that has led to several joint patent applications being filed. This collaboration exists within the Framework Programme 7 European consortium project (NAMASTE) and it involves an appropriate consortium agreement for the protection of intellectual property. My work would also be covered by such an agreement In addition, the School of Physics and Astronomy has a programme for public engagement including outreach visits and lectures for local schools and societies. As a Fellow I will contribute to this programme with lectures related to my own research and nanotechnology.