Prof. Luis Balicas
Florida State University
Origin of topological spin textures in centrosymmetric layered ferromagnets
Location: 1080 Physics Research Building
Faculty Host: Jeanie Lau
Abstract: In this seminar, I will discuss some of our work on centrosymmetric layered ferromagnets1-3 that display topological spin textures, such as skyrmions, merons, etc. despite being centrosymmetric and a priori not subjected to the Dzyaloshinskii–Moriya interaction. For example, Fe3GaTe2 is attracting attention due to its high Curie temperature, low dimensionality, and the presence of topological spin textures above room temperature, making Fe3GaTe2 a good candidate for applications in spintronics. Here, we show, through transmission electron microscopy (TEM) techniques, that Fe3GaTe2 single crystals break local inversion symmetry while maintaining global inversion symmetry according to X-ray diffraction. Coupled to the observation of Néel skyrmions via Lorentz-TEM, our structural analysis provides a convincing explanation for their presence in centrosymmetric materials4,5. Magnetization measurements as a function of the temperature displays a sharp first-order thermodynamic phase-transition leading to a reduction in the magnetic moment. This implies that the ground state of Fe3GaTe2 is globally ferrimagnetic and not a glassy magnetic state composed of ferrimagnetic, and ferromagnetic domains as claimed by other groups. Neutron diffraction studies indicate that the ferromagnetic to ferrimagnetic transition upon reducing the external magnetic field is associated with a change in the magnetic configuration/coupling between Fe1 and Fe2 moments. We observe a clear correlation between the hysteresis observed in both the skyrmion density and the magnetization of Fe3GaTe2. This indicates that its topological spin textures are affected by the development of ferrimagnetism upon cooling. Observation, via magnetic force microscopy, of magnetic bubbles at the magnetic phase boundary suggests skyrmions stabilized by the competition among magnetic phases and distinct exchange interactions. Our study provides an explanation for the observation of Néel skyrmions in centrosymmetric systems, while exposing a correlation between the distinct magnetic phases in Fe3GaTe2 and its topological spin textures. Finally, we will show preliminary data indicating that the coercive fields of Fe3GaTe2 for magnetic fields applied along a planar direction, increase by over one order of magnitude upon exfoliation leading to values comparable to those displayed by commercial hard magnets such as the Nd2Fe14B or Sm2Co17 families of compounds and therefore to a remarkably large magnetic anisotropy at room temperature.6
[1] J. Macy et al., Appl. Phys. Rev. 8, 041401 (2021)
[2] B. W. Casas et al., Adv. Mater. 35, 202212087 (2023).
[3] A. Moon et al., ACS Nano 18, 4216 (2024).
[4] Sang-Eon Lee et al, ACS Nano 19, 28702 (2025).
[5] Sang-Eon Lee et al., Phys. Rev. B 111, 184438 (2025).
[6] L. Mei et al., (unpublished)
Bio: Luis Balicas – Research Professor at FSU Physics Department, and Distinguished University Scholar at the National High Magnetic Field Lab. AAAS and APS fellow, APS outstanding referee. PhD in solid state physics from University of Paris Orsay (now Saclay), advanced master (DEA) in solid state physics. H-Index between 66 (ISI all data bases) or 74 (Google Scholar); ~ 310 publications. Directly supervised over 12 graduate students and a similar number of postdoctoral researchers.
