Magnetic skyrmions offer the prospect of storing information on far smaller scales than existing technologies. In a skyrmion, the orientation of spins rotates progressively from the up direction at the edge of the circular texture, to the down direction at the centre, or vice versa. 

Skyrmions have very specific stability, dynamics and scalability properties that make them well suited for possible applications in novel computing technologies. But this relies on understanding and exploiting different ways of keeping them stable.  

In this paper, published in Physical Review Letters, an international research team has revealed a contributor to this stability for a class of materials that had not previously been understood. 

Most commonly, skyrmions are found in non-centrosymmetric materials, where the stabilisation mechanism is well established. However, they can also be found in highly symmetric rare-earth materials, where the stabilisation mechanism is somewhat controversial, with previous research suggesting a number of different ideas. The magnetic ground states of these materials were also hotly debated. 

By using muon spin spectroscopy on HiFi at ISIS and at the Paul Scherrer Institute, alongside AC susceptibility at Diamond Light Source, the research team have shown that the skyrmions in centrosymmetric Gd₂PdSi₃ can be stabilised by anisotropy. This as was seen from their anisotropic spin dynamics under an applied magnetic field. They have also been able to characterise the magnetic ground states at both higher and lower fields. This led them to discover further intriguing skyrmion-related magnetic phenomena under zero applied field.  

Matjaž Gomilšek, the lead author of the paper, explains “The discovery of anisotropic spin dynamics in Gd₂PdSi₃ should represent a significant step towards finally resolving the puzzling origin of skyrmions and related magnetic phenomena in centrosymmetric materials. For our work, the use of muon spin spectroscopy as a local-probe technique has been crucial.” 

Using HiFi enabled the team to study the spin dynamics in specific magnetic phases that require fields over 1 T. They hope to gain further understanding of the spin dynamics in systems like these by carrying out complementary studies using techniques like inelastic neutron scattering. 

The full paper can be found at DOI: 10.1103/PhysRevLett.134.046702