Tuning magnetic correlations in s=1/2 spin ladder Ba2CuTe1−xWxO6 through site-selective cation substitution

The site-selective substitution of diamagnetic $d^{10}/d^0$ cations offers an efficient way to fine-tune magnetic characteristics by controlling orbital hybridization and superexchange pathways. Herein, we explore the tunability of magnetic properties in coupled spin-ladder compounds $\mathrm{B}{\mathrm{a}}_2\mathrm{CuT}{\mathrm{e}}_{1\text{−}x}{\mathrm{W}}_x{\mathrm{O}}_6$ ($x=0.0-0.30$). The pristine compound exhibits spin-singlet correlations at elevated temperatures, as evidenced by a magnetic susceptibility peak at $T_{\max }\sim 70$ K, Schottky-like specific heat, unconventional magnetic Raman scattering, and a quasilinear decrease in the electron spin resonance linewidth. Notably, the substitution of ${\mathrm{W}}^{6+}$ for $\mathrm{T}{\mathrm{e}}^{6+}$ brings about several marked changes: an increase in the Curie-Weiss temperature, a suppression in the Néel ordering temperature, enhanced magnetic susceptibility at low temperatures, and a weakening of spin-ladder correlations. These modifications collectively suggest that the newly activated exchange interactions through ${\mathrm{W}}^{6+}$ substitution primarily alter intraladder spin topology while amplifying quantum critical fluctuations. This finding highlights the potential for controlling magnetic correlations in spin-ladder compounds through targeted chemical substitution.