Speaker
Description
Terbium gallium garnet (TGG), Tb$_3$Ga$_5$O$_{12}$, is well known for its applications in laser optics, but also for its puzzling low-temperature physics. Its low-temperature ordered structure consists of anisotropic magnetic moments, originating from Tb$^{3+}$ ions sitting on interpenetrating hyperkagome lattices. In this talk we revise these findings thanks to recent time-of-flight neutron powder diffraction experiments, and we contrast them to the picture of the single-ion environment measured via inelastic powder neutron scattering. From a theoretical perspective, we discuss the projection over the effective quasi-doublet ground state of the crystal-field exploiting the general relationship between the local anisotropy and the time-reversal properties of non-Kramers magnetic ions [1]. More specifically for TGG, the structure of the crystal-field states will be analysed with respect to the role they can play in hyperfine-driven phenomena of magnetic ordering [2] as well as in spin-phonon coupling for the thermal Hall effect [3,4].
- J. S. Griffith, Phys. Rev. 132, 316 (1963).
- J. Hamman and P. Manneville, J. Phys. France 34, 615 (1973).
- C. Strohm, G. L. J. A. Rikken, and P. Wyder, Phys. Rev. Lett. 95, 155901 (2005).
- M. Mori, A. Spencer-Smith, O. P. Sushkov, and S. Maekawa, Phys. Rev. Lett. 113, 265901 (2014).
