Lamellar eutectic crystals of Sr 3 Ru 2 O 7 -Sr 4 Ru 3 O 10 have been successfully grown in a double-mirror optical floating zone furnace in the flux feeding floating zone configuration with Ru self-flux. The synthesis procedure of the polycrystalline rod is found to be a critical factor for the crystal growth. The eutectic dark-brown crystals grow in the [100] direction and cleave in the a-b plane as the single phase crystals. The morphology, structure, phase purity, and composition of the samples were analyzed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results from backscattered electron (BSE) imaging as well as from energy dispersive spectrometry (EDS) were combined with the electron backscatter diffraction (EBSD) data to obtain complementary chemical and crystallographic information. Moreover, XRD analysis indicated that the Sr 3 Ru 2 O 7 and Sr 4 Ru 3 O 10 phases match the same crystal with parallel in-plane and out-of-plane lattice parameters. The resistance measurements showed a Fermi liquid behavior at low temperatures analogous to the one found in the single phases. We grew eutectic crystals representing natural junctions made of metamagnetic Sr 3 Ru 2 O 7 and ferromagnetic Sr 4 Ru 3 O 10 that may be useful in studies of possible novel quantum critical phenomena specific to itinerant magnetism systems.
Microsymposia intercalated Na1-xCoO2-x, spin-state transitions of the Co 3+ ion in LaCoO3, a metal-insulator (MI) accompanied by structural transition in LnBaCo2O5.5 (where Ln is a rare earth). We present our recent results on crystal growth of cobaltites: La1-xSrxCoO3 and LnBaCo2O5+x using Optical Travelling Solvent Floating Zone method. The crystals were studied by different techniques and some of results will be discussed. A very small Sr doping level (0.2%) drastically changes magnetic properties of La1-xSrxCoO3 as found using inelastic neutron scattering and magnetisation measurements. This can be explained assuming that the slight hole doping in LaCoO3 matrix creates magnetic polarons, which leads to a spin-state transition of Co 3+. On the background of the spin-state and orbitalordering transitions of the Co 3+ ion in LnBaCo2O5+x, the system shows a metal-insulator transition accompanied by structural one at temperatures above room temperature, three different magnetic phases below room temperature and a structural transition at temperature above MI transition. All these properties can be tuned by a kind of the rare earth ion and oxygen stoichiometry. Structural, magnetic and transport studies of layered cobaltites LnBaCo2O5.5 (Ln=Tb, Nd) especially near metal-insulator transition will be presented.
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