462 research outputs found
Possible link of a structurally driven spin flip transition and the insulator-metal transition in the perovskite LaBaCoO
The complex nature of the magnetic ground state in LaACoO
(A = Ca, Sr, Ba) has been investigated via neutron scattering. It was
previously observed that ferromagnetic (FM) as well as antiferromagnetic (AFM)
correlations can coexist prior to the insulator-metal transition (IMT). We
focused on a unique region in the Ba phase diagram, from x = 0.17 - 0.22, in
which a commensurate AFM phase appears first with a propagation vector, k = (0,
-0.5, 0.5), and the Co moment in the (001) plane of the rhombohedral
lattice. With increasing x, the AFM component weakens while an FM order appears
with the FM Co moment directed along the (001) (=(111)) axis. By x
= 0.22, a spin flip to new FM component appears as the crystal fully transforms
to an orthorhombic (Pnma) structure, with the Co moments pointing along a new
direction, (001) (=(110)). It is the emergence of the magnetic Pnma
phase that leads to IMT.Comment: 5 page
Spin-orbit coupling inactivity of Co ion in geometrically frustrated magnet GeCoO
We report single-crystal neutron diffraction studies on a spinel
antiferromagnet GeCoO, which exhibits magnetic order with a trigonal
propagation vector and tetragonal lattice expansion () below
K. For this inconsistency between spin and lattice in symmetry,
magnetic Bragg reflections with a tetragonal propagation vector were discovered
below . We discuss spin and orbital states of Co ion
underlying the new magnetic component.Comment: 3 pages 2 figures, submitted to ICFCM proceeding (Journal of Physics:
Conference Series, 2011
An Intermediate-band imaging survey for high-redshift Lyman Alpha Emitters: The Mahoroba-11
We present results of our intermediate-band optical imaging survey for
high- Ly emitters (LAEs) using the prime focus camera, Suprime-Cam,
on the 8.2m Subaru Telescope. In our survey, we use eleven filters; four
broad-band filters (, , , and ) and seven
intermediate-band filters covering from 500 nm to 720 nm; we call this imaging
program as the Mahoroba-11. The seven intermediate-band filters are selected
from the IA filter series that is the Suprime-Cam intermediate-band filter
system whose spectral resolution is . Our survey has been made in a
sky area in the Subaru XMM Newton Deep Survey
field. We have found 409 IA-excess objects that provide us a large photometric
sample of strong emission-line objects. Applying the photometric redshift
method to this sample, we obtained a new sample of 198 LAE candidates at . We found that there is no evidence for evolution of the number density
and the star formation rate density for LAEs with between and 5.Comment: 46 pages, 15 figures, PASJ, Vol.57, No.6, in pres
Oral pathobiont induces systemic inflammation and metabolic changes associated with alteration of gut microbiota.
Periodontitis has been implicated as a risk factor for metabolic disorders such as type 2 diabetes, atherosclerotic vascular diseases, and non-alcoholic fatty liver disease. Although bacteremias from dental plaque and/or elevated circulating inflammatory cytokines emanating from the inflamed gingiva are suspected mechanisms linking periodontitis and these diseases, direct evidence is lacking. We hypothesize that disturbances of the gut microbiota by swallowed bacteria induce a metabolic endotoxemia leading metabolic disorders. To investigate this hypothesis, changes in the gut microbiota, insulin and glucose intolerance, and levels of tissue inflammation were analysed in mice after oral administration of Porphyromonas gingivalis, a representative periodontopathogens. Pyrosequencing revealed that the population belonging to Bacteroidales was significantly elevated in P. gingivalis-administered mice which coincided with increases in insulin resistance and systemic inflammation. In P. gingivalis-administered mice blood endotoxin levels tended to be higher, whereas gene expression of tight junction proteins in the ileum was significantly decreased. These results provide a new paradigm for the interrelationship between periodontitis and systemic diseases
Pseudogap Phase Boundary in Overdoped Bi_2Sr_2CaCu_2O_8 Studied by Measuring Out-of-plane Resistivity under the Magnetic Fields
The characteristic pseudogap temperature T* in Bi2Sr2CaCu2O8 system has been
systematically evaluated as a function of doping, especially focusing on its
overdoped region, by measuring the out-of-plane resistivity under the magnetic
fields. Overdoped samples have been prepared by annealing TSFZ-grown
Bi2Sr2CaCu2O8 single crystals under the high oxygen pressures (990 kgf/cm2). At
a zero field, the out-of-plane resistivity showed a metallic behavior down to
Tc (= 62 K), while under the magnetic fields of over 3 T,it showed typical
upturn behavior from around 65 K upon decreasing temperature. This result
suggests that the pseudogap and superconductivity are different phenomena.Comment: 2 pages, 2 figures. Final version accepted for the Proceedings of the
M2S-IX Conference (Tokyo, September 2009
Magnetic field effect on Fe-induced short-range magnetic correlation and electrical conductivity in BiPbSrCuFeO
We report electrical resistivity measurements and neutron diffraction studies
under magnetic fields of
BiPbSrCuFeO, in which hole
carriers are overdoped. This compound shows short-range incommensurate magnetic
correlation with incommensurability , whereas a Fe-free compound
shows no magnetic correlation. Resistivity shows an up turn at low temperature
in the form of and shows no superconductivity. We observe reduction
of resistivity by applying magnetic fields (i.e., a negative magnetoresistive
effect) at temperatures below the onset of short-range magnetic correlation.
Application of magnetic fields also suppresses the Fe induced incommensurate
magnetic correlation. We compare and contrast these observations with two
different models: 1) stripe order, and 2) dilute magnetic moments in a metallic
alloy, with associated Kondo behavior. The latter picture appears to be more
relevant to the present results.Comment: 7 pages, 5 figure
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