Magnetic order and disorder in a quasi-two-dimensional quantum Heisenberg antiferromagnet with randomized exchange

Xiao, F.; Blackmore, W.J.A.; Huddart, B.M.; Gomilšek, M.; Hicken, T.J.; Baines, C.; Baker, P.J.; Pratt, F.L.; Blundell, S.J.; Lu, H.; Singleton, J.; Gawryluk, D.; Turnbull, M.M.; Krämer, K.W.; Goddard, P.A.; Lancaster, T.

Abstract

We present an investigation of the effect of randomizing exchange coupling strengths in the S = 1/2 square lattice quasi-two-dimensional quantum Heisenberg antiferromagnet (QHAF) (QuinH)2Cu(ClxBr1−x )4 · 2H2O (QuinH = Quinolinium, C9H8N+), with 0 x 1. Pulsed-field magnetization measurements allow us to estimate an effective in-plane exchange strength J in a regime where exchange fosters short-range order, while the temperature TN at which long-range order (LRO) occurs is found using muon-spin relaxation, allowing us to construct a phase diagram for the series. We evaluate the effectiveness of disorder in suppressing TN and the ordered moment size, and we find an extended disordered phase in the region 0.4 x 0.8 where no magnetic order occurs. The observed critical substitution levels are accounted for by an energetics-based competition between different local magnetic orders. Furthermore, we demonstrate experimentally that the ground-state disorder is driven by quantum effects of the exchange randomness, which is a feature that has been predicted theoretically and has implications for other disordered quasi-two-dimensional QHAFs.

Citation

Xiao, F., Blackmore, W., Huddart, B., Gomilšek, M., Hicken, T., Baines, C., …Lancaster, T. (2020). Magnetic order and disorder in a quasi-two-dimensional quantum Heisenberg antiferromagnet with randomized exchange. Physical Review B, 102(17), Article 174429. https://doi.org/10.1103/physrevb.102.174429

• Journal Article Type: Article
• Acceptance Date: Oct 26, 2020
• Online Publication Date: Nov 17, 2020
• Publication Date: Nov 1, 2020
• Deposit Date: Nov 18, 2020
• Publicly Available Date: Oct 26, 2021
• Journal: Physical Review B
• Print ISSN: 2469-9950
• Electronic ISSN: 2469-9969
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 102
• Issue: 17
• Article Number: 174429
• DOI: https://doi.org/10.1103/physrevb.102.174429
• Public URL: https://durham-repository.worktribe.com/output/1250761