Quantifying symmetric exchange in ultrathin ferromagnetic films with chirality

Quantifying symmetric exchange in ultrathin ferromagnetic films with chirality

Physical Review B

10.1103/PhysRevB.107.094405

http://dx.doi.org/10.1103/physrevb.107.094405

Tobias Böttcher, T. S. Suraj, Xiaoye Chen, Banibrato Sinha, Hui Ru Tan, Hang Khume Tan, Robert Laskowski, Burkard Hillebrands, Mikhail Kostylev, Khoong Hong Khoo, Anjan Soumyanarayanan, Philipp Pirro

08 March 2023

Böttcher, T., Suraj, T. S., Chen, X., Sinha, B., Tan, H. R., Tan, H. K., Laskowski, R., Hillebrands, B., Kostylev, M., Khoo, K. H., Soumyanarayanan, A., & Pirro, P. (2023). Quantifying symmetric exchange in ultrathin ferromagnetic films with chirality. Physical Review B, 107(9). https://doi.org/10.1103/physrevb.107.094405

The symmetric (Heisenberg) exchange interaction is fundamental to magnetism and assumes critical importance in designing magnetic materials for novel emergent phenomena and device applications. However, quantifying exchange is extremely challenging for ultrathin magnetic films, as techniques and approximations reliably used for bulk materials are largely inapplicable in the two-dimensional limit. Here we present and contrast the measurement of exchange stiffness 𝐴 by several methods on a series of five Co/Pt-based ultrathin (1–2 nm) films. We compare results from (a) spin-wave spectroscopy by Brillouin light scattering, (b) three analytical models describing the temperature dependence of magnetization obtained by magnetometry, (c) microscopic domain periodicity measurements and simulations, and (d) ab initio density functional theory calculations. While different methods present some qualitatively consistent trends across samples, we note, for any given sample, considerable differences (up to 5×) in the absolute values of 𝐴 across the techniques, consistent with discrepancies of 𝐴 reported in literature for nominally similar samples. We analyze possible sources of the discrepancies across various methods, notably including their relationship to the spin-wave dispersion, and the wave-vector ranges probed. We compare the strengths and limitations of the techniques, and outline directions for their future use in characterizing exchange interactions in ultrathin films.

Publisher Copyright

We acknowledge the support of the National Supercomputing Centre (NSCC), Singapore for computational resources. This work was supported by the SpOT-LITE program (A*STAR Grant No. A18A6b0057) funded by Singapore’s RIE2020 initiatives, and by NUS funds (Grant No. A-0004544-00-00). Funding by the Deutsche Forschungsgemeinschaft within the CRC TRR173 Spin+X [No. 268565370 (Projects B01 and B11)] and within the Priority Program SPP2137 Skyrmionics (Project No. 403512431) is gratefully acknowledged.

https://oar.a-star.edu.sg/communities-collections/articles/20583

2469-9969
2469-9950

Institute of Materials Research and Engineering