Structure, spin correlations and magnetism of the $S = 1/2$ square-lattice antiferromagnet Sr$_2$CuTe$_{1-x}$W$_x$O$_6$ ($0 \leq x \leq 1$)

Otto H. J. Mustonen; Ellen Fogh; Joseph A. M. Paddison; Lucile Mangin-Thro; Thomas Hansen; Helen Playford; Maria Diaz-Lopez; Peter Babkevich; Sami Vasala; Maarit Karppinen; Edmund J. Cussen; Henrik M. Rønnow; Helen C. Walker

doi:10.1021/acs.chemmater.3c02535

arXiv · 2309.14422

Structure, spin correlations and magnetism of the $S = 1/2$ square-lattice antiferromagnet Sr$_2$CuTe$_{1-x}$W$_x$O$_6$ ($0 \leq x \leq 1$)

Otto H. J. Mustonen·Ellen Fogh·Joseph A. M. Paddison·Lucile Mangin-Thro·Thomas Hansen·Helen Playford·Maria Diaz-Lopez·Peter Babkevich·Sami Vasala·Maarit Karppinen·Edmund J. Cussen·Henrik M. Rønnow·Helen C. Walker

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Abstract

Quantum spin liquids are highly entangled magnetic states with exotic properties. The $S = 1/2$ square-lattice Heisenberg model is one of the foundational models in frustrated magnetism with a predicted, but never observed, quantum spin liquid state. Isostructural double perovskites Sr$_2$CuTeO$_6$ and Sr$_2$CuWO$_6$ are physical realizations of this model, but have distinctly different types magnetic order and interactions due to a $d^{10}/d^0$ effect. Long-range magnetic order is suppressed in the solid solution Sr$_2$CuTe$_{1-x}$W$_x$O$_6$ in a wide region of $x = 0.05-0.6$, where the ground state has been proposed to be a disorder-induced spin liquid. Here we show that the spin-liquid-like $x = 0.2$ and $x = 0.5$ samples have distinctly different local spin correlations, which suggests they have different ground states. Furthermore, the previously ignored interlayer coupling between the square-planes is likely to play a role in the suppression of magnetic order on the W-rich side at $x \approx 0.6$. These results highlight the complex magnetism of Sr$_2$CuTe$_{1-x}$W$_x$O$_6$ and hint at a new quantum critical point at $x \approx 0.3$.

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Otto H. J. Mustonen, Ellen Fogh, Joseph A. M. Paddison, Lucile Mangin-Thro, Thomas Hansen, Helen Playford, Maria Diaz-Lopez, Peter Babkevich, Sami Vasala, Maarit Karppinen, Edmund J. Cussen, Henrik M. Rønnow, Helen C. Walker. 2023-09-25. Structure, spin correlations and magnetism of the $S = 1/2$ square-lattice antiferromagnet Sr$_2$CuTe$_{1-x}$W$_x$O$_6$ ($0 \leq x \leq 1$). https://doi.org/10.1021/acs.chemmater.3c02535

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