Investigation of structural and magnetic properties of MnTa2O6-based compounds

The structural and magnetic properties of MnTa2O6, Cr0.5Mn0.5Ta2O6, and Fe0.5Mn0.5Ta2O6 compounds prepared using solid-state reaction have been investigated. The x-ray diffraction data indicates that the parent compound MnTa2O6 has an orthorhombic crystal structure with space group Pbcn, whereas the compounds substituted with Fe2+ and Cr2+ both crystallize in tetragonal structure. The thermomagnetic measurement shows that the parent compound is antiferromagnetic with the Néel temperature of 6 K. The samples substituted with Fe2+ and Cr2+ also remain antiferromagnetic with Néel temperatures of 6.5 and 5 K respectively. The Curie-Weiss fitting of the thermomagnetic curves in the paramagnetic region shows a negative Curie-Weiss temperature for all the samples consistent with the antiferromagnetic ordering. The effective magnetic moment estimated from this analysis is 6 μB/f.u., close to the theoretically expected value for the parent compound, 5.2 μB/f.u. and 5.6 μB/f.u. for the Cr2+ and Fe2+ substituted compounds, respectively. In the isothermal magnetization curve measured at 2 K, a spin-flop transition from one antiferromagnetic state to another is observed in MnTa2O6 near 2.4 T. In Cr0.5Mn0.5Ta2O6, no signature of spin-flop transition is observed, but in Fe0.5Mn0.5Ta2O6, it shifts to higher field (5.1 T).