Reduction of critical field for magnetic and orbital-ordering phase transition in impurity-substituted Nd0.45_{0.45}Sr0.55_{0.55}MnO3_3 crystal

We have investigated the Mn-site substitution effect in Nd$_{0.45}$Sr$_{0.55}$MnO$_3$ single crystal, which has an $A$-type layered antiferromagnetic ($A$-AFM) phase with the 3$d_{x^2-y^2}$-type orbital-order. Substitution of Fe or Ga for Mn-site suppresses both the $A$-AFM order and competing ferromagnetic (FM) correlation whereas Cr substitution suppresses only the $A$-AFM order but reactivates the underlying FM correlation via double-exchange mechanism along the AFM coupled $c$-direction. In Nd$_{0.45}$Sr$_{0.55}$Mn$_{0.95}$Cr$_{0.05}$O$_3$, the $A$-AFM state with the orbital-order is changed into the orbital-disordered three-dimensional FM metallic state by applying magnetic field of $\mu_0 H = 12$ T, which is much smaller than that of the parent compound Nd$_{0.45}$Sr$_{0.55}$MnO$_3$.Comment: 5 pages, 4 figures, to appear in APL Material

Electron- and Hole-Doping Effects on AA-site Ordered NdBaMn2_2O6_6

We have investigated electron- and hole-doping effects on $A$-site ordered perovskite manganite NdBaMn$_2$O$_6$, which has the $A$-type (layered) antiferromagnetic (AFM) ground state. Electrons (holes) are introduced by partial substitution of Ba$^{2+}$ (Nd$^{3+}$) with Nd$^{3+}$ (Ba$^{2+}$). Electron-doping generates ferromagnetic (FM) clusters in the $A$-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 $A$-type AFM phase is robust against the hole-doping, and no FM correlation is observed in the hole-doped NdBaMn$_2$O$_6$.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

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

Enhancement of the anomalous Hall effect and spin glass behavior in the bilayered manganite La(2-2x)Sr(1+2x)Mn2O7

The Hall resistivity and magnetization have been investigated in the ferromagnetic state of the bilayered manganite La(2-2x)Sr(1+2x)Mn2O7 (x=0.36). The Hall resistivity shows an increase in both the ordinary and anomalous Hall coefficients at low temperatures below 50K, a region in which experimental evidence for the spin glass state has been found in a low magnetic field of 1mT. The origin of the anomalous behavior of the Hall resistivity relevant to magnetic states may lie in the intrinsic microscopic inhomogeneity in a quasi-two-dimensional electron system.Comment: 7 pages, 4 figures, Solid State Communications (in press

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

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

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

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 TbBaCo$_{2}$O$_{5.5}$ is revealed on the basis of density functional theory calculations. An antiferromagnetic (AFM) superexchange coupling between the almost high-spin Co$^{3+}$ 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 LnBa$_{1-x}$A$_{x}$Co$_{2}$O$_{5+\delta}$ (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