Low-dimensional magnetism of BaCuTe2O6

X-ray diffraction, thermodynamic measurements, and density-functional band-structure calculations are used to study the magnetic behavior of BaCuTe2O6, a member of the ACuTe(2)O(6) structural family that hosts complex three-dimensional frustrated spin networks with possible spin-liquid physics. Temperature-dependent magnetic susceptibility and heat capacity of the Ba compound are well described by the one-dimensional spin-1/2 Heisenberg chain model reminiscent of the Sr-analog SrCuTe2O6. While the intrachain coupling J/kB similar or equal to 37K is reduced compared to 49 K in the Sr compound, the Neel temperature increases from 5.5 K (Sr) to 6.1 K (Ba). Unlike the Sr compound, BaCuTe2O6 undergoes only one magnetic transition as a function of temperature and shows signatures of weak spin canting. We elucidate the microscopic difference between the Sr and Ba compounds and suggest that one of the interchain couplings changes sign as a result of negative pressure caused by the Sr/Ba substitution. The Neel temperature of BaCuTe2O6 is remarkably insensitive to the magnetic dilution with Zn2+ up to the highest reachable level of about 20 %.