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., Baker, P., Pratt, F., Blundell, S., Lu, H., Singleton, J., Gawryluk, D., Turnbull, M., Krämer, K., Goddard, P., & 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