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Orbital Character of the Spin-Reorientation Transition in TbMn6Sn6



S. X. Riberolles, Tyler Slade, Rebecca Dally, P. Sarte, Bing Li, Tianxiong Han, H. Lane, C. Stock, H. Bhandari, N. J. Ghimire, D. Abernathy, P. Canfield, Jeffrey Lynn, B. Ueland, R. McQueeney


TbMn6Sn6 is a topological ferrimagnet where the uniaxial anisotropy of the Tb3+ ion generates out-of-plane magnetization of the ferromagnetic Mn kagome layer, resulting in the emergence of a two-dimensional Chern state. TbMn6Sn6 is also known to possess a high-temperature spin-reorientation (SR) transition at TSR = 310 K from uniaxial to easy-plane collinear ferrimagnetism. Control of the spin-reorientation transition can enable topological switching applications by closing the Chern gap. Here we use inelastic neutron scattering to describe the spin excitations and the fundamental nature of the SR transition. Due to a combination of the crystal-field potential and Tb-Mn magnetic coupling, we conclude that the Tb ion has an effective two-state orbital character, with a uniaxial ground state and an isotropic excited state. Tb ions can be found randomly in either quantum state with a thermally-driven population. At temperatures between 100 K and TSR, the simultaneous observation of a high-energy collective Tb magnon mode and a low-energy Tb orbital exciton, which are split by the magnetic anisotropy energy, is identical to that expected of a spatially-random orbital alloy. Ultimately, a thermally-driven critical concentration of isotropic Tb ions triggers the SR transition.
Nature Communications


topological, spin-reorientation, spin-wave, exciton, neutron scattering, random-phase approximation, ferrimagnet


Riberolles, S. , Slade, T. , Dally, R. , Sarte, P. , Li, B. , Han, T. , Lane, H. , Stock, C. , Bhandari, H. , Ghimire, N. , Abernathy, D. , Canfield, P. , Lynn, J. , Ueland, B. and McQueeney, R. (2023), Orbital Character of the Spin-Reorientation Transition in TbMn6Sn6, Nature Communications, [online], (Accessed March 5, 2024)
Created May 9, 2023, Updated January 23, 2024