The A(2+)Mn(5)(SO4)(6) family of triangular lattice, ferrimagnetic sulfates

A new family of anhydrous sulfates, A(2+)Mn(5)(SO4)(6) (A = Pb, Ba, Sr) is reported. The crystal structures of PbMn5(SO4)(6) and SrMn5(SO4)(6) are solved by powder X-ray and neutron diffraction. BaMn5(SO4)(6) is isostructural. PbMn5(SO4)(6) Crystallizes with P (3) over bar symmetry and unit cell parameters of a = 14.551 (1) angstrom and c = 7.535(1) angstrom. The structure has rich features, including dimers of face-sharing MnO6 octahedra, and two complementary triangular layers of Mn atoms. All compounds undergo a magnetic ordering transition at 10 K, below which, the magnetic susceptibility of the compounds varies systematically with the radius of the non-magnetic cation. Low temperature neutron diffraction shows that the complementary triangular layers result in a ferrimagnet with a net moment corresponding to one high spin Mn2+ per unit cell, correlating well with the magnetization data. The non-magnetic variant PbMg5(SO4)(6) is also reported. (C) 2009 Elsevier Inc. All rights reserved.