307 research outputs found
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
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
Sustainable wastewater management in Indonesia's fish processing industry: Bringing governance into scenario analysis
The government of Indonesia has pledged to meet ambitious greenhouse gas mitigation goals in its Nationally Determined Contribution as well as reduce water pollution through its water management policies. A set of technologies could conceivably help achieving these goals simultaneously. However, the installation and widespread application of these technologies will require knowledge on how governance affects the implementation of existing policies as well as cooperation across sectors, administrative levels, and stakeholders. This paper integrates key governance variables--involving enforcement capacity, institutional coordination and multi-actor networks--into an analysis of the potential impacts on greenhouse gases and chemical oxygen demand in seven wastewater treatment scenarios for the fish processing industry in Indonesia. The analysis demonstrates that there is an increase of 24% in both CH4 and CO2 emissions between 2015 and 2030 in the business-as-usual scenario due to growth in production volumes. Interestingly, in scenarios focusing only on strengthening capacities to enforce national water policies, expected total greenhouse gas emissions are about five times higher than in the business-as-usual in 2030; this is due to growth in CH4 emissions during the handling and landfilling of sludge, as well as in CO2 generated from the electricity required for wastewater treatment. In the scenarios where there is significant cooperation across sectors, administrative levels, and stakeholders to integrate climate and water goals, both estimated chemical oxygen demand and CH4 emissions are considerably lower than in the business-as-usual and the national water policy scenarios
Charge and Orbital Ordering and Spin State Transition Driven by Structural Distortion in YBaCo_2O_5
We have investigated electronic structures of antiferromagnetic YBaCo_2O_5
using the local spin-density approximation (LSDA) + U method. The charge and
orbital ordered insulating ground state is correctly obtained with the strong
on-site Coulomb interaction. Co^{2+} and Co^{3+} ions are found to be in the
high spin (HS) and intermediate spin (IS) state, respectively. It is considered
that the tetragonal to orthorhombic structural transition is responsible for
the ordering phenomena and the spin states of Co ions. The large contribution
of the orbital moment to the total magnetic moment indicates that the
spin-orbit coupling is also important in YBaCo_2O_5.Comment: 4 pages including 4 figures, Submitted to Phys. Rev. Let
Magnetic Structures of High Temperature Phases of TbBaCo2O5.5
Neutron diffraction studies have been carried out on a single crystal of
oxygen-deficient perovskite TbBaCo2O5.5 in the temperature range of 7-370 K.
There have been observed several magnetic or structural transitions. Among
these, the existence of the transitions to the insulating phase from the
metallic one at ~340 K, to the one with the ferromagnetic moment at ~280 K and
possibly to the antiferromagnetic one at ~260 K, with decreasing temperature T
correspond to those reported in former works. We have studied the magnetic
structures at 270 K and 250 K and found that all Co3+ ions of the CoO6
octahedra are in the low spin state and those of the CoO5 pyramids carry spins
which are possibly in the intermediate spin state. Non-collinear magnetic
structures are proposed at these temperatures. Two other transitions have also
been observed at the temperatures, ~100 K and ~250 K.Comment: 9 pages, 2 tables, 10 figure
Synchronization of multi-phase oscillators: An Axelrod-inspired model
Inspired by Axelrod's model of culture dissemination, we introduce and
analyze a model for a population of coupled oscillators where different levels
of synchronization can be assimilated to different degrees of cultural
organization. The state of each oscillator is represented by a set of phases,
and the interaction --which occurs between homologous phases-- is weighted by a
decreasing function of the distance between individual states. Both ordered
arrays and random networks are considered. We find that the transition between
synchronization and incoherent behaviour is mediated by a clustering regime
with rich organizational structure, where some of the phases of a given
oscillator can be synchronized to a certain cluster, while its other phases are
synchronized to different clusters.Comment: 6 pages, 5 figure
Structural Disorder Induced Polaron Formation and Magnetic Scattering in the Disordered Holstein-Double Exchange Model
In this paper we present results on the disordered Holstein-Double Exchange
model, explicitly in three dimension and `metallic' densities, obtained by
using a recently developed Monte Carlo approach. Following up on our earlier
paper, cond-mat/0406085, here we provide a detailed microscopic picture of the
thermally driven metal-insulator transition (MIT) that arises close to the
ferromagnet to paramagnet transition in this problem. This paper is focused
mainly on the `diagnostics', clarifying the origin of the effective disorder
that drives the MIT in this system. To that effect, we provide results on the
thermal evolution of the distributions of (i) lattice distortions, (ii) the net
`structural disorder' and (iii) the `hopping disorder' arising from spin
randomness feeding back through the Hunds coupling. We suggest a phenomenology
for the thermally driven MIT, viewing it as an `Anderson-Holstein' transition.Comment: 6 pages, latex, JPSJ style, 7 eps figs. Style files included.
Proceedings of the SPQS Meeting at Sendai, Japan, 2004. To appear in JPS
Perturbative calculation of the spin-wave dispersion in a disordered double-exchange model
We study the spin-wave dispersion of localized spins in a disordered
double-exchange model using the perturbation theory with respect to the
strength of the disorder potential. We calculate the dispersion upto the
next-leading order, and extensively examine the case of one-dimension. We show
that in that case, disorder yields anomalous gapped-like behavior at the Fermi
wavenumber of the conduction electrons.Comment: 9 pages, 5 figure
Spin state and phase competition in TbBaCo_{2}O_{5.5} and the lanthanide series LnBaCo_{2}O_{5+\delta} (0<=\delta<=1)
A clear physics picture of TbBaCoO is revealed on the basis of
density functional theory calculations. An antiferromagnetic (AFM)
superexchange coupling between the almost high-spin Co ions competes
with a ferromagnetic (FM) interaction mediated by both p-d exchange and double
exchange, being responsible for the observed AFM-FM transition. And the
metal-insulator transition is accompanied by an xy/xz orbital-ordering
transition. Moreover, this picture can be generalized to the whole lanthanide
series, and it is predicted that a few room-temperature magnetoresistance
materials could be found in LnBaACoO
(Ln=Ho,Er,Tm,Yb,Lu; A=Sr,Ca,Mg).Comment: 13 pages, 2 figures; to be published in Phys. Rev. B on 1st Sept.
Title and Bylines are added to the revised versio
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