Geometrical frustration in magnetic systems is defined as an impossibility to satisfy simultaneously all interactions between neighboring sites due to the geometry of the problem. The basic example is the planar triangular network of spins coupled with antiferromagnetic interactions. In the Ising limit, the frustration leads to a high degeneracy of the ground state, which was classified as a classical spin liquid. On the contrary, in the Heisenberg limit, quantum fluctuations play a major role and the quantum spin liquid, a state of matter with long-range quantum entanglement may emerge. In this talk, I will report two of our recent discoveries on hexaaluminates EuAl₁₂O₁₉ and AMgAl₁₁O₁₉ (A = La-Gd), which harbor both a planar triangular lattice of rare earth magnetic ions and a planar triangular lattice of electric dipoles AlO₅ [1-3]. In the first part of the talk, I will demonstrate the realization of electric dipole frustration in EuAl₁₂O₁₉ and I will discuss its analogy with the Ising triangular lattice antiferromagnet [2]. In the second part, I will discuss the nature of the quantum magnetic ground state of CeMgAl₁₁O₁₉ based on magnetization and specific heat measurements down to dilution temperature. Our data confirm partially the recent claim that the strong spin-orbit coupling induces a large anisotropy of the magnetic interaction implying the proximity to quantum criticality between antiferromagnetism and ferromagnetism [4].

References

[1] G. Bastien, Q. Courtade, A. Eliáš, T. Haidamak, P. Proschek, M. Dušek, J. Priessnitz, P. Baláž, R. Colman, Phys. Rev. B, 110, 094436 (2024)

[2] G. Bastien, D. Repček, A. Eliáš, A. Kancko, Q. Courtade, T. Haidamak, M. Savinov, V. Bovtun, M. Kempa, K. Carva, M. Vališka, P. Doležal, M. Kratochvílová, S. A. Barnett, P. Proschek, J. Prokleška, C. Kadlec, P. Kužel, R. H. Colman, and S. Kamba, Adv. Mater. 36, 2410282 (2024)

[3] S. Kumar, M. Klicpera, A. Eliáš, M. Kratochvílová, K. Załęski, M. Śliwińska-Bartkowiak, R. H. Colman and G. Bastien, arXiv preprint arXiv:2410.07885 (2024)

[4] B. Gao, T. Chen, C. Liu, M. L. Klemm, S. Zhang, Z. Ma, X. Xu, C. Won, G. T. McCandless, N. Murai, S. Ohira-Kawamura, S. J. Moxim, J. T. Ryan, X. Huang, X. Wang, J. Y. Chan, S.-W. Cheong, O. Tchernyshyov, L. Balents , and P. Dai, arXiv preprint arXiv:2408.15957 (2024)