Spinning into the future : polarised neutrons help unravel the mysteries of skyrmions

Sub-atomic particles, nuclei and atoms possess intrinsic properties such as their mass or charge. In addition, they are also characterised by their spin, which correponds to an angular momentum.

Vortices of spins are known as skyrmions and are promising candidates for application in spintronic devices. By exploiting the spin of electrons, spintronics can store several bits of information on one single magnetic domain and do not require electron movement for information transport. This is in contrast to current data storage options where separate storage domains are used for each bit.

Spintronic devices are therefore expected to be more efficient at storing data while consuming less energy than the options currently available on the market.

In view of this promising perspective, skyrmions of the magnetic multilayer material [Pt(1 nm)/(CoFeB(0.8 nm)/Ru(1.4 nm)]¹⁰  were investigated by a group of researchers at the ILL using small-angle neutron scattering on D33.

"We saw that the skyrmions were less stable at temperatures below 250 K (about -20°C). We attribute this finding to magnetic anisotropy in the CoFeB layer of the complex multilayer structure", explains Victor Ukleev, the first author of the study. In addition, the team observed only one particular type of skyrmions, namely so-called "Néel-type" ones. In this type of skyrmions, the spins rotate in radial planes outward from the centre of the skyrmion to its periphery. This is in contrast to so-called Bloch-type skyrmions in which the spins rotate perpendicularly to their radial directions. "We were delighted to see that these results align well with theoretical models of such systems", says Ukleev.

These findings represent very important, detailed insights into the structure and properties of materials which are candidates for spintronic devices. "The highly specialised sample environment and characteristics of D33, notably its excellent aptitude for experiments relying on polarised neutrons, are crucial for this type of experiment", explains Robert Cubitt, ILL scientist and main responsible of D33.