MnGeO3 single crystals have been grown by a flux method. The obtained MnGeO3 is orthorhombic; a Pbca space group does not undergo any structural phase transitions in the range from room temperature to 900 °C. Magnetic measurements carried out for the first time on the MnGeO3 single crystal have revealed higher values (TN = 38 K and θ = –100 K) as compared to the data for polycrystalline samples reported in the literature (TN = 10 K and 14 K, θ = –54 K and –46 K). These magnetic parameters for polycrystalline samples synthesized by us are close to the literature data. A Mössbauer spectrum taken at T = 300 K for a sample containing 5% Fe257O3 shows that manganese ions, Mn2+, occupy two nonequivalent positions and iron is included in a sublattice as Fe2+ and distributed among two positions substituting Mn2+. In this study, the magnetic characteristics are shown to be sensitive even to minor impurity amounts. The MnGeO3 magnetic structure and one of possible reasons causing the effect of impurities on the MnGeO3 magnetic properties are considered in the framework of a simple indirect coupling model. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The transport properties of a novel foamed superconductor Bi1.8Pb0.3Sr1.9Ca2Cu3Ox have been studied. As the analysis of resistive transitions in a magnetic field shows, the dissipation follows a thermally activated flux creep model with the temperature-independent pinning potential in S–N–S-type Josephson junctions.

The current report is devoted to the further study of magnetic properties of MnGeO(3) single crystals with orthorhombic symmetry Pbca. New data from magnetic measurements in magnetic fields up to 80 kOe are presented. A spin flop transition is observed at H(sf) = 35 kOe and T = 4.2 K along the a-axis. The exchange and anisotropy fields are determined. The magnetic structure of MnGeO(3) with T(N)≈36 K is qualitatively described using a two-sublattice model.

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