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arXiv · 2004.02547

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

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

We present an investigation of the effect of randomizing exchange strengths in the $S=1/2$ square lattice quasi-two-dimensional quantum Heisenberg antiferromagnet (QuinH)$_2$Cu(Cl$_{x}$Br$_{1-x}$)$_{4}\cdot$2H$_2$O (QuinH$=$Quinolinium, C$_9$H$_8$N$^+$), with $0\leq x \leq 1$. 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 $T_{\mathrm{N}}$ 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 $T_{\mathrm{N}}$ and the ordered moment size and find an extended disordered phase in the region $0.4 \lesssim x \lesssim 0.8$ where no magnetic order occurs, driven by quantum effects of the exchange randomness.

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F. Xiao, W. J. A. Blackmore, B. M. Huddart, M. Gomilšek, T. J. Hicken, C. Baines, P. J. Baker, F. L. Pratt, S. J. Blundell, H. Lu, J. Singleton, D. Gawryluk, M. M. Turnbull, K. W. Krämer, P. A. Goddard, T. Lancaster. 2020-04-06. Magnetic order and disorder in a quasi-two-dimensional quantum Heisenberg antiferromagnet with randomized exchange. https://doi.org/10.1103/physrevb.102.174429

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