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Next Quantum Materials Seminar/ LANEF:


Wednesday, December 13th 2023 at 2:00 pm

Philipp Gegenwart  (Universität Augsburg, Germany)

“ Kagome spin ice HoAgGe “




To access this seminar:

Institut Néel CNRS, Bâtiment K, Room Rémy Lemaire  (K223)


Abstract: Spin ice denotes a novel state of matter, arising in certain geometrically frustrated magnets that do not have a single minimal-energy state but rather fulfill an ice constraint, leading to highly degenerate local spin configurations. While three-dimensional pyrochlore spin ice is well established, its two-dimensional counterpart “Kagome spin ice”, with 2 in-1 out or 1 in-2-out ice rule, leading to a honeycomb lattice of positive/negative magnetic monopoles, was only studied on artificial nanorods of ferromagnet films. The rare-earth intermetallic HoAgGe has non-Kramers 4f10 moments on a distorted kagome lattice with the four lowest CEF modes contributing to magnetism at low temperatures. Remarkably the in-plane magnetization at low temperatures reveals a series of metamagnetic transitions separating fractional magnetization plateaus. Refinement of single crystal neutron diffraction reveals that all these states fulfill the kagome ice rule, establishing HoAgGe as first crystalline kagome spin ice [1]. Magnetotransport and anomalous Hall effect (AHE) show pronounced signatures related to the transitions between the fractional magnetization plateaus. They allow to distinguish domains with opposite toroidal orders and differing AHE yet similar magnetization, implying a hidden time-reversal-like degeneracy, related to the non-trivial distortion of the kagome lattice in HoAgGe [2]. We also discuss emergent quantum magnetism in the low-T c-axis magnetization.

Work in collaboration with Kan Zhao and Hua Chen.


[1]  K. Zhao, H. Deng, H. Chen, K.A. Ross, V. Petricek, G. Günther, M. Russina, V. Hutanu, P. Gegenwart: Realization of the kagome spin ice state in a frustrated intermetallic compound, Science 367, 1218 (2020).
[2]  K. Zhao, Y. Tokiwa, H. Chen, P. Gegenwart: Time-reversal-like degeneracies distinguished by the anomalous Hall effect in a metallic kagome ice compound, Nature physics, to be published.

The organizers:

Elsa Lhotel (elsa.lhotel@neel.cnrs.fr)
Florence Levy-Bertrand (florence.levy-bertrand@neel.cnrs.fr)