Spin dynamics and field-induced magnetic phase transition in the honeycomb Kitaev magnet α−Li2IrO3

Choi, Sungkyun; Manni, S.; Singleton, J.; Topping, C.V.; Lancaster, T.; Blundell, S.J.; Adroja, D.T.; Zapf, V.; Gegenwart, P.; Coldea, R.

doi:10.1103/physrevb.99.054426

Spin dynamics and field-induced magnetic phase transition in the honeycomb Kitaev magnet α−Li2IrO3

Choi, Sungkyun; Manni, S.; Singleton, J.; Topping, C.V.; Lancaster, T.; Blundell, S.J.; Adroja, D.T.; Zapf, V.; Gegenwart, P.; Coldea, R.

Authors

Sungkyun Choi

S. Manni

J. Singleton

C.V. Topping

Professor Tom Lancaster tom.lancaster@durham.ac.uk
Professor

S.J. Blundell

D.T. Adroja

V. Zapf

P. Gegenwart

R. Coldea

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.

Citation

Choi, S., Manni, S., Singleton, J., Topping, C., Lancaster, T., Blundell, S., …Coldea, R. (2019). Spin dynamics and field-induced magnetic phase transition in the honeycomb Kitaev magnet α−Li2IrO3. Physical Review B, 99(5), Article 054426. https://doi.org/10.1103/physrevb.99.054426

Journal Article Type	Article
Acceptance Date	Jan 23, 2019
Online Publication Date	Feb 25, 2019
Publication Date	Feb 1, 2019
Deposit Date	Feb 26, 2019
Publicly Available Date	Mar 8, 2019
Journal	Physical Review B
Print ISSN	2469-9950
Electronic ISSN	2469-9969
Publisher	American Physical Society
Peer Reviewed	Peer Reviewed
Volume	99
Issue	5
Article Number	054426
DOI	https://doi.org/10.1103/physrevb.99.054426
Related Public URLs	https://arxiv.org/abs/1810.03212

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Copyright Statement
Reprinted with permission from the American Physical Society: 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 © 2019 by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modified, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.