SKM 2023 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 21: Spin-Dependent Phenomena in 2D
MA 21.4: Vortrag
Dienstag, 28. März 2023, 15:45–16:00, HSZ 403
Magnetism and THz excitations in quasi-2D systems perturbed by external fields — •Karel Carva and Krishna K. Pokhrel — Charles University, Faculty of Mathematics and Physics, DCMP, Ke Karlovu 5, 121 16 Prague 2, Czech Republic
Systems with a very weak exchange coupling between magnetically ordered layers represent an interesting intermediate stage between the well-known isotropic bulk magnets and the recently intensively studied 2D magnets [1]. We perform a complex investigation of lattice and magnetic excitations induced by external perturbations in such quasi-2D system, trihalide VI3, employing the synergy of DFT calculations, infrared, THz, and Raman spectroscopies [2]. The transition to the long-range ferromagnetic order is accompanied by the observed variations of phonon frequencies indicating strong magnetoelastic coupling. The acoustic magnon mode acquires here unusually high energy reaching to the THz range, but dramatically softens at temperatures where a second lattice distortion has been reported. First-principles calculations also show the strong connection of magnetic ordering and anisotropy to the lattice and its low temperature distortions [3]. These findings suggest the possibility of controlling magnetic anisotropy in this system by selective occupation of specific lattice modes. In this way magnon spectra would be strongly modified as well. We also show changes induced by strong magnetic fields in VI3 and similar systems.
[1] M. Gibertini et al., Nat. Nanotech. 14, 408 (2019)
[2] D. Hovančík et al., J. Phys. Chem. Lett. 13, 11095 (2022)
[3] L. M. Sandratskii, K. Carva, Phys. Rev. B 103, 214451 (2021)