Skyrmionics: Magnetic skyrmions

Chirality is commonly found in nature, and is characterized by a reflection asymmetry. A simple example being that our left hand is the mirror opposite of our right. When this appears in the structure of atoms in a solid, it affects the way that the magnetic moments of unpaired electrons organize themselves through the relativistic spin-orbit Dzyaloshinskii-Moriya (DM) interaction. This interaction is usually weak; nevertheless, it induces qualitatively different behaviour. In chiral magnets, such as MnSi, the Dzyaloshinskii-Moriya interaction stabilises non-collinear arrangements of the magnetic moments and emergent phenomena like the topologically protected magnetic defects called skyrmions. The latter are in the focus of theoretical and experimental studies because their small size, stability and emergent electromagnetism make them ideal candidates for spintronics applications.

The work within NPM2 focusses on high resolution neutron scattering investigations of chiral magnets and skyrmion hosting materials in conjunction with magnetisation and susceptibility measurements. Within the Netherlands the work is performed in collaboration with the University of Groningen. A great deal of the neutron scattering experiments take place at the LARMOR instrument at ISIS, UK,  at ISIS Neutron and Muon Source, which is a UK-NL joint venture supported by a NWO-Groot grant of the Dutch Science foundation. The experiments involve multidisciplinary and multinational research teams. A most recent publication of a team of  Researchers from the Institute Laue Langevin in France, ISIS Neutron and Muon Source at the UK, Ames Lab in USA under the lead of the Delft University of Technology team appeared in Physical Review Letters. By combining Small Angle Neutron Scattering (SANS) as shown in the figure above and high resolution Neutron Spin Echo (NSE) spectroscopy,  the team monitored the influence of a magnetic field on the chiral magnetic correlations both in space and in time. The SANS measurements were performed on LARMOR, and were part of the commissioning programme. 

Recent Publications

Magnetic Fluctuations, Precursor Phenomena, and Phase Transition in MnSi under a Magnetic Field; Pappas C., Bannenberg L. J., Lelièvre-Berna E., Qian F., Dewhurst C. D., Dalgliesh R. M., Schlagel D. L., Lograsso T. A., and Falus P.; 
 Phys. Rev. Lett. 119, 182 (2017).

Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi; Bannenberg, L. J., Kakurai K., Falus P., Lelièvre-Berna E., Dalgliesh R. Dewhurst C. D., Qian F, Onose Y., Endoh Y., Tokura Y,. Pappas C.; Phys Rev B 95, 144433 (2017).

Magnetic relaxation phenomena in the chiral magnet Fe1-xCoxSi : An ac susceptibility study; Bannenberg L. J., Lefering A. J. E., Kakurai K., Onose Y., Endoh Y., Tokaura Y., and Pappas C; Phys Rev B 94, 134433 (2016). 

Extended skyrmion lattice scattering and long-time memory in the chiral magnet Fe1−xCoxSi; Bannenberg, L. J., Kakurai K., Qian F., Lelièvre-Berna E, Dewhurst C. D., Onose Y., Endoh Y., Tokura Y. and Pappas C.
; Phys Rev B 94, 104406 (2016). 

Phase diagram and magnetic relaxation phenomena in Cu2OSeO3; Qian F., Wilhelm H., Aqeel A., Palstra T. T. M., Lefering A. J. E., Brück E. H. and Pappas C.; Phys Rev B 94, 064418 (2016).