Multi-modal electron microscopy of 3D racetrack memory
Lead Research Organisation:
University of Glasgow
Department Name: School of Physics and Astronomy
Abstract
Modern society is becoming increasingly reliant on digital data, yet most data is stored on magnetic hard disk drives that consume large amounts of energy and are limited in reliability. As data centres and volumes of servers grow it is becoming necessary to explore more efficient future digital storage technologies.
Domain wall (DW) memory is a type of solid-state magnetic random-access memory that controls the motion and position of magnetic domains along a nano-scale magnetic track, i.e., racetrack (RT) memory. The magnetic moments of DWs are driven by transferring spin angular momentum from electrons in an applied current pulse. The position of the DWs can also be controlled by including defects along the RT that hold the DWs in place between current pulses.
Conventional RT memories can vastly improve their storage density and connectivity if they expand into three-dimensional (3D) RT systems. However, this makes their fabrication and understanding the behaviour of DWs very challenging due to reduced access.
The aim of this project is to use advanced electron microscopy techniques to construct 3D RT memories that provide direct, nano-scale analysis of their chemistry, structure and DW motion under operando conditions (current pulsing and heating). This will allow effective engineering of their operation, taking the functional performance of 3D RTs into a brand-new realm of understanding. Through optimising the composition, geometrical design and current pulse parameters of the 3D RTs we can address the key issue of consistent, power-efficient control of DWs motion in complex 3D nanomagnetic arrays.
The results will not only lead to high impact publications and conference presentations, but also provide a wealth of information for expanding the field of spintronics into advanced nanomagnetic systems with complex 3D geometries.
Domain wall (DW) memory is a type of solid-state magnetic random-access memory that controls the motion and position of magnetic domains along a nano-scale magnetic track, i.e., racetrack (RT) memory. The magnetic moments of DWs are driven by transferring spin angular momentum from electrons in an applied current pulse. The position of the DWs can also be controlled by including defects along the RT that hold the DWs in place between current pulses.
Conventional RT memories can vastly improve their storage density and connectivity if they expand into three-dimensional (3D) RT systems. However, this makes their fabrication and understanding the behaviour of DWs very challenging due to reduced access.
The aim of this project is to use advanced electron microscopy techniques to construct 3D RT memories that provide direct, nano-scale analysis of their chemistry, structure and DW motion under operando conditions (current pulsing and heating). This will allow effective engineering of their operation, taking the functional performance of 3D RTs into a brand-new realm of understanding. Through optimising the composition, geometrical design and current pulse parameters of the 3D RTs we can address the key issue of consistent, power-efficient control of DWs motion in complex 3D nanomagnetic arrays.
The results will not only lead to high impact publications and conference presentations, but also provide a wealth of information for expanding the field of spintronics into advanced nanomagnetic systems with complex 3D geometries.
People |
ORCID iD |
| Trevor Almeida (Principal Investigator) |
| Title | 3-Dimensional Model Based Iterative Reconstruction of Magnetisation |
| Description | Methods for characterisation of 3D magnetic spin structures are necessary to advance the performance of 3D magnetic nanoscale technologies. However, as the component dimensions approach the nanometre range, it becomes more challenging to analyse 3D magnetic configurations with the appropriate spatial resolution. Here, we developed a method based on Lorentz transmission electron microscopy in which model-based iterative reconstruction (MBIR) is used to reconstruct the most probable magnetisation in an exemplar nanostructure. This method is based on relating electron phase measurements to the magnetic configuration of the nanostructure, and therefore, the method is subject to certain limitations. In this proof-of-concept experiment, MBIR was tested on an L-shaped ferromagnetic cobalt nanowire, fabricated using focused electron beam induced deposition (FEBID). Off-axis electron holography was used to acquire a tomographic tilt series of electron holograms, which were analysed to measure magnetic electron phase shift over two tilt arcs with up to ±60? tilt range. Then, a 3D magnetisation vector field consistent with the tomographic phase measurements was reconstructed, revealing multiple magnetic domains within the nanowire. The reconstructed magnetisation is accurate for magnetic domains larger than 50 nm, and higher resolution can be achieved by the continued development of tomographic reconstruction algorithms. |
| Type Of Material | Data analysis technique |
| Year Produced | 2024 |
| Provided To Others? | No |
| Impact | This model is currently under review in a journal, but a large impact is anticipated in the coming years. |
| Description | Collaboration with HoMMage Collaborative Research Centre/Transregio (CRC/TRR) 270 in Germany |
| Organisation | Ernst Ruska-Centre (ER-C) for Microscopy and Spectroscopy with Electrons |
| Country | Germany |
| Sector | Private |
| PI Contribution | As part of the collaboration and visit to Juelich, we developed a 3-Dimensional Model Based Iterative Reconstruction of Magnetisation that can be applied directly to the hard magnets investigated in this larger German collaboration grant. |
| Collaborator Contribution | The Ernst Ruska-Centre provided access to their microscope from which we acquired large datasets, as well as value expertise in the development of this technique |
| Impact | Two journals papers that were output from this collaboration are currently under review. This collaboration is not currently multi-disciplinary, as it focuses on electron microscopy of magnetic materials. |
| Start Year | 2024 |