Some aspects of antiferromagnetic ordering in LiMnP0.85V0.15O4: Neutron diffraction and DC-magnetization studies

V-substituted LiMnPO₄ has been synthesized by the solid state reaction route. Combined Rietveld refinement of neutron and X-ray data revealed that all vanadium ions are located in the same positions as the phosphorus ions. The magnetic structure of LiMnP_0.85V_0.15O₄ was found to be the same as that described for undoped antiferromagnetic LiMnPO₄ (T_N=34.5 K). DC-magnetization measurements were carried out to study the peculiarities of magnetic ordering in LiMnP_0.85V_0.15O₄. An irreversible behavior of DC magnetization was found at magnetic fields less than ∼2 kOe. It was demonstrated that an increase in the magnitude of the applied field leads to a reduction of the discrepancy between zero-field-cooled and field-cooled processes. These effects were explained by the movement of domain walls and by transition of the system to a monodomain state. The anomaly in the magnetization vs field dependence attributed presumably to the spin-flop transition was observed at ∼40 kOe. The existence of magnetic inhomogeneity in the paramagnetic phase of LiMnP_0.85V_0.15O₄ was proved by the analysis of the χ?T product. It was concluded that the observed changes in χ?T are indicative of a competition between ferromagnetic and antiferromagnetic correlations at temperatures slightly exceeding T_N.