437 research outputs found
Comparative study of ordered and disordered Y1-xSrxCoO3-d
We have succeeded in preparing A-site ordered- and disordered-Y1/4Sr3/4CoO3-d
with various oxygen deficiencies delta, and have made comparative study of
their structural and physical properties. In the A-site ordered structure,
oxygen vacancies order, and d = 0.34 sample shows a weak ferromagnetic
transition beyond 300 K. On the other hand, in the A-site disordered structure,
no oxygen vacancy ordering is observed, and d = 0.16 sample shows a
ferromagnetic metallic transition around 150 K. A-site disordering destroys the
orderings of oxygen-vacancies and orbitals, leading to the strong modification
of the electronic phases.Comment: 3 pages, 3 figures, proceeding of 52nd Mangetism and Magnetic
Materials Conference (MMM 2007), published in Journal of Applied Physic
Electron- and Hole-Doping Effects on -site Ordered NdBaMnO
We have investigated electron- and hole-doping effects on -site ordered
perovskite manganite NdBaMnO, which has the -type (layered)
antiferromagnetic (AFM) ground state. Electrons (holes) are introduced by
partial substitution of Ba (Nd) with Nd (Ba).
Electron-doping generates ferromagnetic (FM) clusters in the -type AFM
matrix. With increasing the electron-doping level, the volume fraction of the
FM phase or the number of the FM clusters is abruptly increasing. In contrast,
the -type AFM phase is robust against the hole-doping, and no FM correlation
is observed in the hole-doped NdBaMnO.Comment: 8 pages, 5 figures, to be published in Journal of the Physical
Society of Japa
Magnetic-field-induced switching between ferroelectric phases in orthorhombic-distortion-controlled MnO
We have investigated the dielectric and magnetic properties of
EuYMnO the presence of the 4 magnetic
moments of the rare earth ions, and have found two ferroelectric phases with
polarization along the and axes in a zero magnetic field. A magnetic
field induced switching from one to the other ferroelectric phase took plase in
which the direction of ferroelectric polarization changed from the a axis to
the c axis by the application of magnetic fields parallel to the a axis. In
contrast to the case of TbMnO, in which the 4 moments of Tb
ions play an important role in such a ferroelectric phase switching, the
magnetic-field-induced switching between ferroelectric phases in
EuYMnO does not originate from the magnetic
transition of the rare-earth 4 moments, but from that of the Mn 3 spins.Comment: 8 pages, 3 figures, RevTeX4, Proceedings of MMM 2005, to appear in J.
Appl. Phy
Pressure induced transition from a spin glass to an itinerant ferromagnet in half doped manganite Ln0.5Ba0.5MnO3 (Ln=Sm and Nd) with quenched disorder
The effect of quenched disorder on the multiphase competition has been
investigated by examining the pressure phase diagram of half doped manganite
Ln0.5B0.5MnO3 (Ln = Sm and Nd) with A-site disorders. Sm0.5Ba0.5MnO3, a spin
glass insulator at ambient pressure, switches to a ferromagnetic metal with
increasing pressure, followed by a rapid increase of the ferromagnetic
transition temperature Tc. The rapid increase of Tc was confirmed also for
Nd0.5Ba0.5MnO3. These observations indicate that the unusual suppression of the
multicritical phase boundary in the A-site disordered system, previously
observed as a function of the averaged A-site ionic radius, is essentially
controlled by the pressure and hence the band width. The effect of quenched
disorder is therefore much enhanced with approaching the multicritical region.Comment: 4 pages including 3 figure
Structure-related transport properties of A-site ordered perovskite Sr3ErMn4-xGaxO10.5-d
We report x-ray diffraction, resistivity, thermopower, and magnetization of
Sr3ErMn4-xGaxO10.5-d, in which A-site ordered tetragonal phase appears above
x=1, and reveal that the system exhibits typical properties seen in the
antiferromagnetic insulator with Mn3+. We succeed in preparing both A-site
ordered and disordered phases for x=1 in different preparation conditions, and
observe a significant decrease of the resistivity in the disordered phase. We
discuss possible origins of the decrease focusing on the dimensionality and the
disordered effect.Comment: 4 pages, 6 figure
Investigation and Comparison between New Satellite Impact Test Results and NASA Standard Breakup Model
This paper summarizes two new satellite impact tests conducted in order to investigate on the outcome of low- and hyper-velocity impacts on two identical target satellites. The first experiment was performed at a low velocity of 1.5 km/s using a 40-gram aluminum alloy sphere, whereas the second experiment was performed at a hyper-velocity of 4.4 km/s using a 4-gram aluminum alloy sphere by two-stage light gas gun in Kyushu Institute of Technology. To date, approximately 1,500 fragments from each impact test have been collected for detailed analysis. Each piece was analyzed based on the method used in the NASA Standard Breakup Model 2000 revision. The detailed analysis will conclude: 1) the similarity in mass distribution of fragments between low and hyper-velocity impacts encourages the development of a general-purpose distribution model applicable for a wide impact velocity range, and 2) the difference in area-to-mass ratio distribution between the impact experiments and the NASA standard breakup model suggests to describe the area-to-mass ratio by a bi-normal distribution
A-site Randomness Effect on Structural and Physical Properties of Ba-based Perovskite Manganites
The discovery of novel structural and physical properties in the -site
ordered manganite BaMnO ( = Y and rare earth elements) has
demanded new comprehension about perovskite manganese oxides. In the present
study, the -site disordered form, BaMnO, has been
investigated and compared with both BaMnO and
MnO (: Sr, Ca) in the structures and electromagnetic
properties. BaMnO has a primitive cubic perovskite cell
in the structure and magnetic glassy states are dominant as its ground state,
in contrast to the ordinary disordered MnO (: Sr, Ca).
In Pr-compounds with various degrees of Pr/Ba randomness at the -sites, the
-site disorder gradually suppresses both ferromagnetic and A-type
antiferromagnetic transitions and finally leads to a magnetic glassy state in
PrBaMnO. A peculiar behavior, multi-step magnetization
and resistivity change, has been observed in PrBaMnO.
These properties could be closely related to any spatial heterogeneity caused
by the random distribution of Ba and with much different
ionic radius.Comment: 9 pages, to be published in J. Phys. Soc. Jpn. 73 Aug. (2004
An Origin of CMR: Competing Phases and Disorder-Induced Insulator-to-Metal Transition in Manganites
We theoretically explore the mechanism of the colossal magnetoresistance in
manganese oxides by explicitly taking into account the phase competition
between the double-exchange ferromagnetism and the charge-ordered insulator. We
find that quenched disorder causes a drastic change of the multicritical phase
diagram by destroying the charge-ordered state selectively. As a result, there
appears a nontrivial phenomenon of the disorder-induced insulator-to-metal
transition in the multicritical regime. On the contrary, the disorder induces a
highly-insulating state above the transition temperature where charge-ordering
fluctuations are much enhanced. The contrasting effects provide an
understanding of the mechanism of the colossal magnetoresistance. The obtained
scenario is discussed in comparison with other theoretical proposals such as
the polaron theory, the Anderson localization, the multicritical-fluctuation
scenario, and the percolation scenario.Comment: 16 pages, 7 figures, submitted to Wandlitz Days on Magnetism:
Local-Moment Ferromagnets: Unique Properties for Modern Application
Successful Treatment for Hepatic Encephalopathy Aggravated by Portal Vein Thrombosis with Balloon-Occluded Retrograde Transvenous Obliteration
This report presents the case of a 78-year-old female with hepatic encephalopathy due to an inferior mesenteric venous-inferior vena cava shunt. She developed hepatocellular carcinoma affected by hepatitis C virus-related cirrhosis and underwent posterior sectionectomy. Portal vein thrombosis developed and the portal trunk was narrowed after hepatectomy. Portal vein thrombosis resulted in high portal pressure and increased blood flow in an inferior mesenteric venous-inferior vena cava shunt, and hepatic encephalopathy with hyperammonemia was aggravated. The hepatic encephalopathy aggravated by portal vein thrombosis was successfully treated by balloon-occluded retrograde transvenous obliteration via a right transjugular venous approach without the development of other collateral vessels
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