Project

Nanomagnetism; Spin Torque; Domain Walls; Magnetic Solitons; Vortices; Magnetic Imaging; Magnetotransport; Spin-polarized currents; Spin Transfer Torque

Lead
Lay summary
Modern information and communication technology relies on fast processing of data but also on storing large quantities of information that need to be accessed quickly. So fast, high capacity, low form factor and low power non-volatile memories are a crucial enabler of today's IT. They are already an important part of all electronic systems, representing a growing market segment, and should increase their importance in the future en route towards the "Storage everywhere" society. Magnetic storage has been prevalent in the form of hard disk drives with massive capacity but slow access times. Rather than using conventional field-induced switching of such memories, recently alternative approaches based for instance on switching by magnetic domain wall motion have been put forward (race track memory device).The fundamental physics underlying fast wall displacement in a magnetic wire when spin-polarized currents are injected is only starting to be revealed. This proposal tackles the major open questions of the fundamental magnetotransport in confined spin structures with varying magnetization gradients. We suggest a number of complementary robust methods, which allow for the first time the unambiguous measurement the spin torque terms that arise due to the interaction between spin-polarized charge carriers and the magnetization and lead to spin dynamics. We extend the work on domain walls to other magnetic soliton spin structures to probe the universality of the dynamics that is governed by the topological winding numbers that describe the spin structures.This might then lead to novel spin configurations that could be used in future storage or logic devices, which are non-volatile and thus energy-saving.

Direct link to Lay Summary

Last update: 21.02.2013

Active participation

Self-organised

Active participation

Title	Year

Number	Title	Start	Funding scheme

In this project the dynamics of magnetic topological soliton spin structures, such as domain walls will be investigated and by inducing the dynamics using injected spin-polarized currents, the fundamental interplay between spin-polarized charge carriers and the magnetization will be determined. Static and dynamic imaging of simple solitons such as domain walls and vortices will be extended to more complex bubble solitons and the dynamics will be correlated with the topological winding number to probe the universal behaviour that is predicted to be governed just by the topology of the spin structure.The dynamics can be induced by injecting currents that lead to novel spin transfer torque effects, as the spin-polarized current interacts with the magnetic spin structure. To understand this interaction and validate the present contradicting theories, a range of robust and complementary experiments supplemented by theoretical simulations is proposed that allows one to unambiguously and quantitatively determine the torque terms. The experiments will be extended from the well-known 3d metals to exciting other materials, where larger effects are expected, such as rare earth compounds, highly anisotropic multilayers and in particular highly spin-polarized materials classes. Correlating the observed effects with the materials properties will yield the details of the interaction between the spin - polarized charge carriers and the magnetization, which in most materials is far from being understood and the validity and limits of the presently used theoretical models will be tested.The systems will be optimized to judge the potential for applications including storage, sensing and logic as well as for spin torque domain wall oscillators.