MnSnTeO: A Chiral Antiferromagnet Prepared by a Two-Step Topotactic Transformation.

MnSnTeO, a new chiral antiferromagnet, was prepared both by topotactic transformation of the metastable rosiaite-type polymorph and by direct synthesis from coprecipitated hydroxides. Its structure and its static and dynamic magnetic properties were studied comprehensively both experimentally (through X-ray and neutron powder diffraction, magnetization, specific heat, dielectric permittivity, and ESR techniques) and theoretically (by means of density functional theory (DFT) calculations within the spin-polarized generalized gradient approximation). MnSnTeO is isostructural with MnSbO (space group 321) and does not show any structural transition between 3 and 300 K. The magnetic susceptibility and specific heat exhibit an antiferromagnetic ordering at ≈ 9.8 K, which is confirmed by low-temperature neutron data. At the same time, the thermodynamic parameters demonstrate an additional anomaly on the temperature dependences of magnetic susceptibility χ(), specific heat () and dielectric permittivity ε() at * ≈ 4.9 K, which is characterized by significant temperature hysteresis. Clear enhancement of the dielectric permittivity at * is most likely to reflect the coupling of dielectric and magnetic subsystems leading to development of electric polarization. It was established that the ground state of MnSnTeO is stabilized by seven exchange parameters, and neutron diffraction revealed incommensurate magnetic structure with propagation vector = (0, 0, 0.183) analogous to that of MnSbO. DFT calculations demonstrate that the strongest exchange coupling occurs between planes along diagonals. All exchange parameters are antiferromagnetic and reveal moderate frustration.