Polycrystalline samples of novel oxypnictides, Sr2ScCo1−x Fe x PO3, with Fe-doped Co1−x Fe x P layer were synthesized, and their resistivities and Seebeck coefficients were measured. These materials, ...Sr2ScCo1−x Fe x PO3, crystallize in a layered structure which represent an alternative stack of ThCr2Si2 type Co1−x Fe x layers and K2NiF4 type Sr2ScO3 layers. The resistivities (ρ) decrease with decreasing temperature like a metal. The Seebeck coefficients (S) show negative values at room temperature, while the S show positive values for x = 0.04–0.7 at low temperature.
The iron-based F-doped superconductors LaFeAsO1−xFx with a transition temperature of 24 K (for x 0.07) and 26 K (x 0.11) and its parent material LaFeAsO were studied using 57Fe Mössbauer ...spectroscopy. Further investigation was carried out by applying external magnetic fields. F-doped superconductors showed a singlet pattern with no magnetic splitting throughout the temperature range from 4.2 to 298 K. On the other hand, magnetically-split spectra were observed in the parent LaFeAsO below the Néel temperature of about 140 K. The internal magnetic field reached 5.3 T at 4.2 K. The external magnetic fields up to 14 T were applied to the singlet phases, F-doped superconductors and the parent LaFeAsO above the Néel temperature. The induced magnetically-split spectra showed the internal magnetic fields with the comparable value to the applied fields. This fact confirmed that these singlet phases have the paramagnetic feature. The magnetic fields were also applied to the magnetically-ordered phase of LaFeAsO below the Néel temperature. The evolution of the spectra depending on the external magnetic fields was clearly explained by a model with two sublattice spins of the powdered antiferromagnet. This fact confirmed the magnetically-ordered phase is an antiferromagnet. The spin-flop field was also estimated by the model as about 26 T.
Undoped LaFePnO (Pn P, As) shows metallic resistivity and a tetragonal phase at room temperature. The electrical resistivity (ρ) of undoped LaFeAsO exhibits a sudden decrease around Tanom ∼160 K with ...decreasing the temperature and increases with decreasing the temperatures (T) below another threshold temperature (Tmin). It makes a contrast to undoped LaFePO, which shows neither of Tanom nor Tmin. The Tanom corresponds to a crystallographic phase transition: undoped LaFeAsO shows an orthorhombic phase at temperatures < 160 K. A positive magnetoresistance (MR (ρ-ρ0) / ρ0) also appears below Tanom. DFT calculations indicate that spin moment of LaFeAsO is 1.56 μB / Fe in an antiferromagnetic spin configuration in a tetragonal phase, while spin moment of LaFePO is almost quenched.
We report electrical and magnetic properties of LaTMPO (TM Fe, Ni) under high pressures. From resistivity measurements, superconducting transition temperature Tc for LaFePO and LaNiPO increases ...steeply up to about 0.8 GPa, and the dTc/dP values are more than 4 K/GPa and 1 K/GPa, respectively. From the results of high-pressure x-ray diffraction measurements, the oxypnictide compounds show an anisotropic compression along a-axis and c-axis.
The pressure dependence on the superconducting transition temperature (T c ) was investigated for the iron-based superconductors LaFeAsO1-x F x and SmFeAsO1-x F x . The T c 's increase largely for ...LaFeAsO1-x F x with a small increase of pressure, while a sharp decrease of T c was observed for SmFeAsO1-x F x . The electrical resistivity measurements reveal pressure-induced superconductivity for undoped LaFeAsO and SmFeAsO. These pressure effects seem to be related to an anisotropic decrease of the lattice constants under high pressure from the x-ray diffraction measurements up to 10 GPa for the LaFeAsO1-x F x system.
A Gram-negative, strictly aerobic, motile, filamentous and viscous exopolymer-producing bacterium, designated strain YT21(T), was isolated from fresh water. Phylogenetic analysis of the 16S rRNA gene ...sequence indicated that strain YT21(T) lies within a cluster containing the established genera Segetibacter, Terrimonas, Niastella and Chitinophaga in the phylum Bacteroidetes. However, the isolate represented a lineage distinct from these genera, with sequence similarities ranging from 88.9 to 91.8 %. The genomic G+C content was 45.2 mol%. The predominant isoprenoid quinone was MK-7. The major fatty acids were 15 : 0 iso, 17 : 0 iso 3-OH and 15 : 1 iso G. On the basis of morphological features and phenotypic and phylogenetic data, strain YT21(T) represents a novel genus and species, for which the name Filimonas lacunae gen. nov., sp. nov. is proposed. The type strain of Filimonas lacunae is strain YT21(T) (=NBRC 104114(T) =DSM 21054(T)).
The pressure dependence on the superconducting transition temperature (
T
c
) was investigated for the iron-based superconductors LaFeAsO
1−
x
F
x
and SmFeAsO
1−
x
F
x
. The
T
c
’s increase largely ...for LaFeAsO
1−
x
F
x
with a small increase of pressure, while a sharp decrease of
T
c
was observed for SmFeAsO
1−
x
F
x
. The electrical resistivity measurements reveal pressure-induced superconductivity for undoped LaFeAsO and SmFeAsO. These pressure effects seem to be related to an anisotropic decrease of the lattice constants under high pressure from the x-ray diffraction measurements up to 10 GPa for the LaFeAsO
1−
x
F
x
system.
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