Ladder-like Structural Architecture of Layered Magnetic $A_{2.4}$Cr$_8$Te$_{14}$ ($A$ = Rb, Cs) Compounds by Self-flux Synthesis

Abstract

The discovery and control of intergrowth structures represent an important avenue for the targeted synthesis of new, more complex structure types. When including magnetic framework metal atoms, this enhanced complexity can transfer to rich magnetic ground states. Here, we show that the subtle adjustment of the composition of alkali-tellurium fluxes enables the synthesis of a new family of alkali chromium tellurides, $A_{2.4}$Cr$_8$Te$_{14}$ ($A$ = Rb, Cs). Their ladder-like crystal structures integrate the two-dimensional character of delafossite-like $A$CrTe$_2$ with the tunnel motifs of hollandite-like $A_{x}$Cr$_5$Te$_8$ phases. This results in a previously unobserved unique hybrid framework. Direction-dependent magnetization measurements on oriented single crystals reveal distinct magnetic ground states: Rb$_{2.4}$Cr$_8$Te$_{14}$ is antiferromagnetic with $T_{\rm N}$ = 114.5 K, while Cs$_{2.4}$Cr$_8$Te$_{14}$ is ferrimagnetic with $T_{\rm C}$ = 125.0 K. This work underscores the simplicity and effectiveness of flux growth as a design strategy for discovering low-dimensional materials.