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arXiv · 2306.14082

High-field NMR study of the spin correlations in the spin-cluster mineral Na$_2$Cu$_3$O(SO$_4$)$_3$

Long Ma·J. X. Li·L. S. Ling·Y. Y. Han·L. Zhang·L. Hu·W. Tong·C. Y. Xi·Li Pi
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Abstract

We report NMR study on the spin correlations in the spin-cluster based mineral Na$_2$Cu$_3$O(SO$_4$)$_3$ with magnetic fields ranged from 1 T to 33 T. The long-range magnetic order is observed from both the sudden spectral broadening at $T_N$ and critical slowing down behavior in the temperature dependence of spin-lattice relaxation rates ($1/T_1(T)$). The hump behavior of $1/T_1(T)$ persists to $\mu_0H=7.25$ T, above which a spin excitation gap is observed from the thermally activated temperature dependence of $1/T_1$. The gap size shows a linear field dependence, whose slope and intercept respectively yield an effective magnetic moment of 2.54 $\mu_B$ and a 0.94 meV spin excitation gap under zero magnetic field. These results indicate the existence of short-range order and prominent easy-plane spin anisotropy, which are important for understanding the spin excitation spectrum in A$_2$Cu$_3$O(SO$_4$)$_3$.

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Long Ma, J. X. Li, L. S. Ling, Y. Y. Han, L. Zhang, L. Hu, W. Tong, C. Y. Xi, Li Pi. 2023-06-25. High-field NMR study of the spin correlations in the spin-cluster mineral Na$_2$Cu$_3$O(SO$_4$)$_3$. https://doi.org/10.1103/physrevb.107.245134

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