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arXiv · 1512.01650

Alternating-spin-chain compound AgVOAsO$_4$ probed by $^{75}$As NMR

N. Ahmed·P. Khuntia·H. Rosner·M. Baenitz·A. A. Tsirlin·R. Nath
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Abstract

$^{75}$As NMR measurements were performed on a polycrystalline sample of spin-1/2 alternating-spin-chain Heisenberg antiferromagnet AgVOAsO$_4$. Temperature-dependent NMR shift $K(T)$, which is a direct measure of the intrinsic spin susceptibility, agrees very well with the spin-1/2 alternating-chain model, justifying the assignment of the spin lattice. From the analysis of $K(T)$, magnetic exchange parameters were estimated as follows: the leading exchange $J/k_{\rm B} \simeq 38.4$ K, alternation ratio $α= J'/J \simeq 0.68$, and spin gap $Δ/k_{\rm B} \simeq 15$ K. The transferred hyperfine coupling between the $^{75}$As nucleus and V$^{4+}$ spins obtained by comparing the NMR shift with bulk susceptibility amounts to $A_{\rm hf} \simeq 3.3$ T/$μ_{\rm B}$. Our temperature-dependent spin-lattice relaxation rate $1/T_1(T)$ also shows an activated behaviour at low temperatures, thus confirming the presence of a spin gap in AgVOAsO$_4$.

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N. Ahmed, P. Khuntia, H. Rosner, M. Baenitz, A. A. Tsirlin, R. Nath. 2015-12-05. Alternating-spin-chain compound AgVOAsO$_4$ probed by $^{75}$As NMR. https://doi.org/10.1103/physrevb.96.224423

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