Incommensurate magnetic order arising from frustrated interchain interactions in the spin-1/2 chain compound AgCuVO${}_4$

Quantum spin chains with competing interactions offer a platform where low dimensionality and frustration–both acting to suppress magnetic order–intersect. We studied magnetic ordering in the spin-1/2 chain compound AgCuVO${}_4$ using muon spin spectroscopy and neutron diffraction. Long-range magnetic order emerges at $T_N=2.0(1)$ K, which is $\sim$1/200 of the dominant intrachain coupling $J$ and $\sim$1/15 of the interchain interactions. The collinear incommensurate amplitude-modulated magnetic structure features a reduced ordered moment of 0.13(3) ${\mu }_{\mathrm{B}}$, confined to the $ab$ plane and modulated along the $c$ axis–perpendicular to the spin chains–indicating frustrated interchain couplings. The low $T_N$, small moment, and incommensurate order highlight strong frustration, positioning AgCuVO${}_4$ as a model system for exploring frustration in quantum spin chains.