Sr2V3O9 and Ba2V3O9:: Quasi-one-dimensional spin-systems with an anomalous low temperature susceptibility -: art. no. 174417

The magnetic behavior of the low-dimensional vanadium oxides Sr2V3O9 and Ba2V3O9 was investigated by means of magnetic susceptibility and specific heat measurements. In both compounds, the results can be very well described by an S=1/2 Heisenberg antiferromagnetic chain with an intrachain exchange of J=82 and 94 K in Sr2V3O9 and Ba2V3O9, respectively. In Sr2V3O9, antiferromagnetic ordering at T-N=5.3 K indicate a weak interchain exchange of the order of J(perpendicular to)congruent to2 K. In contrast, no evidence for magnetic order was found in Ba2V3O9 down to 0.5 K, pointing to an even smaller interchain coupling. In both compounds, we observe a pronounced Curie-like increase of chi(T) below 30 K, which we tentatively attribute to a staggered field effect induced by the applied magnetic field. Results of local density approximation calculations support the quasi-one-dimensional character and indicate that in Sr2V3O9, the magnetic chain is perpendicular to the structural one with the magnetic exchange being transferred through VO4 tetrahedra.