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Synthesis, crystal structure and physical properties of quasi-one-dimensional ACr$_3$As$_3$ (A = Rb, Cs)

Recently, new Cr-based superconductors, A$_2$Cr$_3$As$_3$ (A = K, Rb, Cs), have gained a strong interest because of their one-dimensional crystal structures and electron correlations. Here we report the crystal structure and physical properties of two related materials ACr$_3$As$_3$ (A = Rb, Cs) which are synthesized via a soft-chemical A+ deintercalation in A$_2$Cr$_3$As$_3$. The new compounds remain one-dimensional (Cr$_3$As$_3$)$_{\infty}$ linear chains, and the interchain distance can be tuned by the incorporation of the alkali-metal cations with different sizes. The physical-property measurements indicate a local-moment behavior at high temperatures, and the moments freeze into a cluster spin-glass state below 5$\sim$6 K. No superconductivity was observed in both materials. We also found that, with increasing the interchain distance, the Cr effective moments increase monotonically, accompanied with the enhancement of semi-conductivity. Our results shed light on the understanding of occurrence of superconductivity in A$_2$Cr$_3$As$_3$.