Effect of the synthesis atmosphere on the magnetic and structural properties of TbMnO3 multiferroic polycrystals

Nanostructured orthorhombic TbMnO3 polycrystals were synthesized by high-energy ball milling and annealing in Ar or O2 atmospheres. Oxygen annealed samples show shrunken unit cells in comparison with Ar annealed ones, without Mn valence changes in both cases. Magnetic and dielectric investigations show strong evidence of long-range (43 K) and quasi-long-range (9 K) ordering for Mn and Tb ions, respectively, and a noncollinear spin-spiral magnetic ordering of Mn spins, with higher magnetic response and ferroelectric state for argon synthesized samples.