Towards IT of the Future: Interactions of Skyrmions Better Understood

22 October 2018

Tiny magnetic vortices known as skyrmions have the potential to revolutionize computer technology. In maybe 10 or 20 years from now, they could enable to store and process data not just more compactly but also in a significantly more energy efficient way. Nevertheless, before this can become a reality, numerous obstacles must be overcome. For example, what impact do the tiniest, almost unavoidable defects in materials have on the spins? Which interactions arise between skyrmions (or other chiral magnetic structures) and electrons? Two new publications from PGI-1/IAS-1 address these fundamental questions, important for the technical utilization of skyrmions:

Nature Communications: Universality of defect-skyrmion interaction profiles,
Autoren: Imara Lima Fernandes, Juba Bouaziz, Stefan Blügel & Samir Lounis,
DOI: 10.1038/s41467-018-06827-5

Artistic representation of a skyrmion (reddish arrows) and its energy profile.
Forschungszentrum Jülich

Whether skyrmions will one day be used as information carriers depends in part on how they interact with the defects ubiquitous in any device. Defects include, for example, contamination with foreign atoms. These can hinder the motion of the magnetic spin, for example, or prevent it entirely, change its direction and so on.

Dr. Imara Lima Fernandes and her colleagues at PGI-1/IAS-1 have now systematically investigated the extent of the interaction between defects and skyrmions in an extremely computationally intensive ab initio study. For this purpose, they mapped the energy profile of a single skyrmion interacting with impurities made up of a few atoms solely by solving the relevant quantum mechanical equations without involving experimental data.

They discovered that the interaction profile is attributable to the generic function of the number of electrons in the impurity. The shape of the profile can be explained by simple arguments involving, for instance, hybridization mechanisms and the filling of electronic states.

Similarities with key concepts of bond theories in catalysis and surface sciences suggest that this is a universal principle on which predictions can be based concerning the impact of a given defect on skyrmions. The research team anticipates that a better understanding of these correlations will enable the design of devices that utilize implanted surface defects to generate and control skyrmions.

Communications Physics 1, 60 (2018): Engineering chiral and topological orbital magnetism of domain walls and skyrmions,
Autoren: Fabian R. Lux, Frank Freimuth, Stefan Blügel & Yuriy Mokrousov,
DOI: 10.1038/s42005-018-0055-y

If an electron moves adiabatically and slowly through a non-collinear magnetic structure, this can be interpreted as an actual magnetic field in the reference frame of the electron. Because the electron is a charged particle, this magnetic field has an effect on the orbital degree of freedom, i.e. its orbital motion, resulting in orbital magnetization.
Forschungszentrum Jülich

The physicist Fabian Lux and his colleagues at PGI-1/IAS-1 reveal in a recent publication a perspective on how orbital properties of chiral spin systems could one day be manipulated in a precise, targeted manner. With the aid of computer simulations, they discovered that the orbital magnetic properties of skyrmions alter by orders of magnitude when the strength of the spin-orbit-coupling is modified.

Orbital magnetic properties represent a further degree of freedom in addition to electric charge and spin, which technically should one day prove useful for information processing. The corresponding concept is known as “orbitronics”, to reflect both electronics and spintronics. Besides skyrmions, domain walls – the borders between areas of different magnetizations - could also subsequently be used as information carriers.

In terms of their approach, the researchers used a variant of perturbation theory, which applies quantum mechanics to phase space. Intuitively, this appears to some physicists to be impossible, as according to Heisenberg’s uncertainty principle, a quantum state cannot be assigned a defined momentum and a defined position simultaneously.

Further information:

Website of Prof. Dr. Samir Lounis: Functional Nanoscale Structure Probe and Simulation Laboratory (Funsilab)

Website of Prof. Dr. Yuriy Mokrousov Topological Nanoelectronics Group at Forschungszentrum Jülich and at the Johannes-Gutenberg-Universität Mainz

Last Modified: 15.03.2022