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Abstract:

Magnetism in polymeric fullerenes was discussed. A structural and magnetic study of two-dimensional polymerized rhombohedral phase of C60 was described. Electron microscopy and x-ray diffraction studies showed that the buckyballs were undamaged in the most magnetic phase. Results showed that the precise orientations of the buckyballs can be of crucial importance in determining the magnetic ground state.

Abstract:

We report the growth of single crystals of La1-xSrxMnO3 (x = 0.0-0.3) by the floating-zone technique in an image furnace under high argon pressure (6-8 atm). Ail excess of Mn in the polycrystalline starting material was used to compensate for the evaporation during growth. single crystals of diameter 8 mm and length 70 mm have been obtained. The phase purity, composition and quality of the crystals were analysed by X-ray diffraction and electron probe microanalysis. We discuss the effect on the crystal growth of varying the amount of Mn excess and of the composition of the growth atmosphere. We also present magnetization and resistivity data for a few of the samples. (C) 2002 Elsevier Science B.V. All rights reserved.

Abstract:

Oxidation of the ferromagnetic B-site diluted manganese(III) perovskite La2GaMnO6 is investigated by synthesis of the La2-xSrxGaMnO6 series. At the x = 0.3 composition, which corresponds to diamagnetic element substitution at the B-site of metallic LaO.7SrO.3MnO3, the MnIII and MnIV valences order in real space at low temperature with an unusual lamellar motif. Orbital ordering at the MnIII centers in this array maintains ferromagnetism and enhances the static coherent Jahn-Teller distortion over that found for the pure MnIII end-member, facilitating eg electron hopping in the insulating state. Further oxidation to x = 0.5 completely suppresses the charge and orbital ordering, leading to glassy rather than long-range ordered magnetism.