Molten salt synthesis, V-doped and magnetic properties of columbite MnNb2O6

Abstract

A novel molten salt synthsis technology is developed to prepare single phase and V-doped MnNb2O6powder. The prepared samples are characterized by XRD, SEM, EDS, TEM, HRTEM and SAED. The results show that the MnNb2O6 powder has an orthorhombic structure.and the samples prepared in different molten salts exhibit different shapes:flake shape, rod shape, and rectangular shape. The effects of temperature and doped on structure and morphology are discussed. HRTEM and SAED indicate the rod-shape MnNb2O6 has the properties of anisotropic growth and crystalline integrality. Magnetic properties are measured by superconducting quantum interference device (SQUID) in a temperature range of 2—30 K under a magnetic field of 2T. The magnetic measurement results indicate that MnNb1.8V0.2O6 undergoes an antiferromagnetic transition with a Néel temperature of 5.4 K. Above 20 K, the inverse susceptibility is fitted well to the Curie-Weiss law θ=-33.9 K,C=10.52 K emu mol ·f.u.-1 and effective moment 5.82 μ B can be obtained. With V-doped amount increases, antiferromagnetic interaction increases. According to the Anderson model, the MnNb2-xVxO6 is antiferromagnet in a low temperature range, which is induced by the superexchange interaction of Mn2+-O2--Mn2+.