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Durham University

Department of Physics

Staff profile

Publication details for Professor Tom Lancaster

Choi, Sungkyun, Manni, S., Singleton, J., Topping, C. V., Lancaster, T., Blundell, S. J., Adroja, D. T., Zapf, V., Gegenwart, P. & Coldea, R. (2019). Spin dynamics and field-induced magnetic phase transition in the honeycomb Kitaev magnet α−Li2IrO3. Physical Review B 99(5): 054426.

Author(s) from Durham

Abstract

The layered honeycomb iridate α-Li2IrO3 displays an incommensurate magnetic structure with counterrotating moments on nearest-neighbor sites, proposed to be stabilized by strongly frustrated anisotropic Kitaev
interactions between spin-orbit entangled Ir4+ magnetic moments. Here we report powder inelastic neutron
scattering measurements that observe sharply dispersive low-energy magnetic excitations centered at the
magnetic ordering wave vector, attributed to Goldstone excitations of the incommensurate order, as well as
an additional intense mode above a gap 2.3 meV. Zero-field muon-spin relaxation measurements show
clear oscillations in the muon polarization below the Néel temperature TN 15 K with a time-dependent profile
consistent with bulk incommensurate long-range magnetism. Pulsed-field magnetization measurements observe
that only about half the saturation magnetization value is reached at the maximum field of 64 T. A clear
anomaly near 25 T indicates a transition to a phase with reduced susceptibility. The transition field has a Zeeman
energy comparable to the zero-field gapped mode, suggesting gap suppression as a possible mechanism for the
field-induced transition.