In recent years topology (the study of the properties of geometric configurations which are unaltered by certain elastic transformations such as a stretching, bending or twisting) has emerged as a fascinating phenomenon in solid state research from both fundamental and applied perspectives. This is particularly the case for certain magnetisation configurations, where the topology protects the spatial magnetisation or spin arrangement. Due to their unique properties, such topologically-protected spin structures (TSS) have the potential to revolutionise the Information and Communications Technology sector. The goal of this project is to underpin fundamental research in this active field by developing metrological tools and methods for the characterisation of TSS and, thus, support future applications. In addition, the first paths towards new topological quantum standards will be explored.
Need addressed by the project
Fundamental research in the field of spintronics has led both to the recognition of scientific merits at the highest level and to extremely fast development of a huge market sector dealing with mass production of consumer and industrial electronics, such as hard disk storage devices and sensors for mobile phones and cars. The search for new materials featuring room temperature operation, ultralow power consumption, full electrical control, and scalability continues apace. Recently, the study of spin structures with a certain topologically‑protected spin arrangement, has moved into worldwide focus. Despite intensive ongoing research on TSS (such as chiral domain walls which are boundaries between regions of uniform magnetisation with a certain gradual rotation of the magnetisation or skyrmions, which are vortex‑like spin arrangements with diameters typically ranging between several nm to several 100 nm), there are several high-level requirements in this field connecting basic research, metrology, and ability to exploit these structures in novel devices that need to be addressed:
The quest for new materials and systems with stable TSS requires a precise understanding and knowledge of relevant material parameters such as the Dzyaloshinskii-Moriya interaction (DMI) constant. However, validated metrology tools for these parameters do not currently exist.
Due to their nanoscale size, it is difficult to experimentally probe some types of TSS. Therefore, validated measurement methods are needed enabling the identification and manipulation of multiple and individual TSS.
Reliable concepts for the investigation of current- and field‑induced dynamics of TSS at GHz and THz frequencies still have to be developed. In addition, experimental high‑risk‑high‑gain research is required to verify whether TSS enable the realisation of novel quantum standards.
Future research on TSS requires the fabrication of TSS with reproducible topological characteristics. Micromagnetic simulations and analytical tools are required to validate experimental results and to reliably predict novel material properties.
The overall objective of this project is to develop and establish metrological and scientific tools for the characterisation of TSS. This work is expected to significantly contribute to the development of new magnetic storage, spin-logic, and microwave devices in the future well as new quantum standards.
The specific objectives of this project are:
To develop and validate metrology tools and methods for reliable determination of key material parameters of TSS, i.e., the Dzyaloshinskii-Moriya interaction (DMI) constant.
To develop, compare and validate measurement techniques capable of unambiguously identifying and manipulating specific nanometre-scale TSS, such as domain walls, bubbles, and skyrmions in different magnetic materials. These methods will be applicable to both multiple and individual TSS.
To develop methods for the investigation and analysis of novel dynamical and quantisation effects in TSS. This work will capture the dynamics of TSS at GHz and THz frequencies and explore whether TSS might serve as quantum standards at room temperature and low magnetic fields.
To provide protocols for the reproducible growth of materials for experiments on TSS and reliable micromagnetic simulations and analytical tools for the modelling of TSS. The simulations will allow for a comparison with and an interpretation of experimental results.
To implement a research network on TSS in Europe with complementary infrastructure. To develop guidelines for accurate characterisation of TSS and to implement new measurement services on the DMI constant.