title: Magnetic spin structure of pyroxene-type MnGeO(3).
abstract: Polycrystalline MnGeO(3) material was synthesized at 1473 K and ambient pressures using ceramic sintering techniques. Under these conditions the pyroxene-type compound crystallizes in the orthorhombic modification with space group Pbca, as determined from the refinement of the neutron diffraction data. The monoclinic modification, space group C 2/c, was also present at a level of 8.8(4) wt% and the magnetic structures for the two polymorphs at low temperatures have been found simultaneously. The monoclinic form orders magnetically below 34 K; the spin structure can be described using k = (0, 0, 0) in the magnetic space group C 2'/c, having an antiferromagnetic spin arrangement within and between the chains of M1 and M2 sites. The orthorhombic phase of MnGeO(3) transforms to a magnetically ordered state with k = (0, 0, 0) and magnetic space group Pb'c'a below 12 K. Spins on M1 sites are aligned along the crystallographic a-axis with a slight non-collinear antiferromagnetic spin arrangement with and between the M1 chains. Spins on M2 sites are also antiferromagnetically coupled; however, one of the three different M1-M2 superexchange pathways within the band of M1 and M2 sites displays a ferromagnetic interaction, while the other two allow antiferromagnetic interaction.
authors.affiliation: Division of Mineralogy, Department of Materials Engineering and Physics, University of Salzburg, Austria. guenther.redhammer@sbg.ac.at
authors.forename: G J
authors.initials: GJ
authors.lastname: Redhammer
authors.forename: A
authors.initials: A
authors.lastname: Senyshyn
authors.forename: G
authors.initials: G
authors.lastname: Tippelt
authors.forename: G
authors.initials: G
authors.lastname: Roth