Investigating field-induced magnetic phases in TbB4. - (Fabienne Duc / LNCMI / Seminar). - 12/03/2026, 14H
2026-03-12 14:00 - 15:30 (Europe/Paris) | Salle de seminaire du LNCMI, Champs Magnétiques Pulsés, 143 avenue de Rangueil, Toulouse, France
Seminar LNCMI
Fabienne Duc, LNCMI-Toulouse
Seminar LNCMI, 12/03/2026, 14H, LNCMI-Toulouse
Abstract
Neutron diffraction in high magnetic fields offers a powerful and complementary approach to uncover exotic magnetic phases in frustrated systems, providing direct insight into magnetic structures and their field-induced transformations.
This seminar will focus on neutron diffraction studies of TbB4, a tetraboride compound that exhibits a rich phase diagram under applied magnetic fields.
Using the 2 K/40 T pulsed-field cryomagnet, developed through collaboration between LNCMI-Toulouse, ILL-Grenoble, and CEA-Grenoble, we demonstrate how high-field neutron diffraction enables the investigation of complex magnetic structures.
The seminar will highlight the technical progress achieved in performing such experiments, as well as the improvements required for studying materials with small magnetic moments.
Lien Zoom : https://univ-grenoble-alpes-fr.zoom.us/j/94228207316?pwd=[REDACTED]

Magnetoelastic effects in the 2D limit enhanced by intense magnetic fields in CrOC. - (Tristan Riccardi / LNCMI / Seminar). - 19/03/2026, 14H
2026-03-19 14:00 - 15:30
Seminar LNCMI
Tristan Riccardi, LNCMI-Grenoble
Seminar LNCMI, 19/03/2026, 14H, LNCMI, Salle Pauthenet
Abstract
CrOCl is a van der Waals magnet featuring a rich phase diagram [1,2] related to its low-symmetry structure, structural phase transitions, and a subtle competition of interactions potentially leading to magnetic frustration. In a previously published work [3], we showed how, exploiting the strong magneoelastic coupling in the material, we can use Raman scattering spectroscopy, performed at variable temperature and magnetic field, to decipher the magnetic phase diagram of bulk CrOCl.
Here we extend this work to the investigation of thin flakes of CrOCl down to the single layer. While previous works on thin layers have used transport techniques and did not show a clear evolution of the properties with the thickness [4], we were able to highlight strong effects of the coupling of the lattice with the external field, leading to zone-folded phonons (produced by the magnetic supercell) or blue/red-shifts of the phonon energies at the metamagnetic transitions to build a phase diagram of the material at varying thickness. Moreover, we were able to demonstrate the existence of a strong magnetostriction effect at high magnetic field (up to 30T), present for all thicknesses down to the monolayer.
Lien Zoom : https://univ-grenoble-alpes-fr.zoom.us/j/94228207316?pwd=[REDACTED]

References:
[1] P. G. Reuvekamp. Investigation into the magnetic and the structural properties of two low-dimensional
antiferromagnets TiPO4 and CrOCl. 2014
[2] P. Gu & al. Magnetic phase transitions and magnetoelastic coupling in a two- dimensional stripy
antiferromagnet. Nano Letters. 22, 1233–1241. 2022
[3] A. Pawbake & al. Magnetic Phases and Zone-Folded Phonons in a Frustrated van der Waals Magnet.
ACS Nano. 19, 26, 23693–23702. 2025
[4] M. Zhang & al. Spin-Lattice Coupled Metamagnetism in Frustrated van der Waals Magnet CrOCl. Small.
19, 2300964. 2023

Terahertz Magnon-Polariton Control Using a Tunable Liquid Crystal Cavity. - (Dmitriy Yavorskiy / LNCMI / Seminar). - 26/03/2026, 14H
2026-03-26 14:00 - 15:30
Seminar LNCMI
Dmitriy Yavorskiy, Polish Academy of Sciences in Warsaw
Seminar LNCMI, 26/03/2026, 14H, LNCMI, Salle Pauthenet
Abstract
In the strong light–matter coupling regime, polariton modes emerge as hybrid excitations combining electromagnetic cavity modes and material resonances. While magnon–polaritons in ferromagnets have been extensively explored at microwave frequencies, antiferromagnetic systems enable access to the terahertz (THz) range, where strong coupling can be achieved using Fabry–Perot cavities. However, antiferromagnetic magnons are typically tunable only via temperature or high magnetic fields, which limits dynamic control of magnon–polariton states. Here we demonstrate remote electrical control of antiferromagnetic magnon–polaritons by combining an antiferromagnetic crystal with an electrically tunable photonic environment. The system consists of a nickel oxide (NiO) slab, chosen for its low spin damping and temperature-dependent resonance frequency near 1.0 THz above room temperature, placed adjacent to a nematic liquid-crystal cell and separated by a controlled gap of approximately 2.5 mm. The magnon frequency is tuned via the NiO temperature, while an applied electric field reorients the liquid crystal, modifying the cavity-mode frequencies and spatial field distributions. Using terahertz time-domain spectroscopy, we measure reflection spectra as functions of temperature and applied voltage and observe voltage-controlled avoided crossings between cavity modes and magnons, as well as changes in the magnon–photon coupling strength. These results demonstrate remote electrical control of antiferromagnetic magnon–polariton states at room temperature without direct physical contact between the magnetic material and the electrically active element.
Lien Zoom : https://univ-grenoble-alpes-fr.zoom.us/j/94228207316?pwd=[REDACTED]
References:
[1] D. Yavorskiy et al, ACS Photonics 12, 5c01879 (2025)
