Synthesis, structure and magnetic properties of the new mixed-valence vanadate Na2SrV3O9

The new complex oxide Na2SrV3O9 was synthesized and investigated by means of X-ray diffraction, electron microscopy and magnetic susceptibility measurements. This oxide has a monoclinic unit cell with parameters a=5.416(1) A, b=15.040(3) A, c=10.051(2) A, β=97.03(3) deg. , space group P21/c and Z=4. The crystal structure of Na2SrV3O9, as determined from X-ray single-crystal data, is built up from isolated chains formed by square V4+O5 pyramids. Neighboring pyramids are linked by two bridging V5+O4 tetrahedra sharing a corner with each pyramid. The Na and Sr atoms are situated between the chains. Electron diffraction and HREM investigations confirmed the crystal structure. The temperature dependence of the susceptibility indicates low-dimensional magnetic behavior with a sizeable strength of the magnetic intra-chain exchange J of the order of 80 K, which is very likely due to superexchange through the two VO4 tetrahedra linking the magnetic V4+ cations