Effect of Offstoichiometry on the Physical Properties of Sr_2VO_4

摘要

We studied the physical properties of Sr_2VO_4 with a K_2NiF_4 structure in polycrystalline forms synthesized under various different conditions. We found that stoichiometric samples or those with nominal hole doping into the d~1 state of the V ion exhibit insulating behavior with an antiferromagnetic interaction between V moments, whereas those with nominal electron doping exhibit metallic conduction and ferromagnetic interaction. A structural phase transition at T_c ~ 100 K, which is likely to be associated with the orbital ordering of the V~(4+) ion, is observed only in the former sample exhibiting a sharp drop in the magnetic susceptibility at the same temperature, whereas no structural anomaly was observed for the sample exhibiting a cusp in the magnetic susceptibility at ~50 K.