Canted ferrimagnetism in the distorted double perovskite La₃Mn₂NbO₉

The synthesis, structural characterization, and magnetic properties of La3Mn2NbO9 double perovskite are reported. The crystal structure has been refined by X-ray and neutron powder diffraction data in the monoclinic space group P2(1/n). The Mn2+, Mn3+ and Nb5+ cations are distributed at the 2d and 2c Wyckoff sites, with a high cation order degree in the latter, mainly occupied by Mn2+/Mn3+. The Mn3+ presence was established from X-ray Emission Spectroscopy and X-ray Photoelectron Spectroscopy. Rietveld refinements of powder neutron diffraction data show that at room temperature the cell parameters are a = 5.6063(3) angstrom, b = 5.8155(3) angstrom, c = 7.9877(2) angstrom y beta = 89.89(1)degrees. Magnetization measurements indicate the presence of ferromagnetic and antiferromagnetic interactions with T-C-19 K and T-N-11 K, respectively, with a magnetic cell of symmetry Gamma(1)(A(g)). The analysis of the neutron data suggests a canted ferrimagnetic spin structure where an antiferromagnetic unit-cell in a and c axis, and ferromagnetic in b axis with a propagation vector k = (0 1/2 0) was used. The effective magnetic moment obtained experimentally is mu(eff) = 5.50 mu B/mol Mn2+/(3+), slightly lower than the theoretical one for spin only (5.83 mu B). (C) 2020 Elsevier B.V. All rights reserved.