176 research outputs found
Anisotropic effect of Cd and Hg doping on Pauli limited superconductor CeCoIn
We investigated the effect of Cd and Hg doping on the first order
superconducting (SC) transition and the high field-low temperature SC state of
CeCoIn by measuring the specific heat of CeCo(InCd) with x=0.0011, 0.0022 and 0.0033 and CeCo(InHg) with x=0.00016, 0.00032, and 0.00048 at temperatures down to 0.1 K and
fields up to 14 T. Cd substitution rapidly suppresses the cross-over
temperature , where the superconducting transition changes from
second to first order, to =0 K with x=0.0022 for [100], while
it remains roughly constant up to x=0.0033 for [001]. The
associated anomaly of the proposed FFLO state in Hg-doped samples is washed out
by x=0.00048, while remaining at the same temperature, indicating high
sensitivity of that state to impurities. We interpret these results as
supporting the non-magnetic, possibly FFLO, origin of the high field - low
temperature state in CeCoIn
Bonding, Moment Formation, and Magnetic Interactions in Ca14MnBi11 and Ba14MnBi11
The ``14-1-11'' phase compounds based on magnetic Mn ions and typified by
Ca14MnBi11 and Ba14MnBi11 show unusual magnetic behavior, but the large number
(104) of atoms in the primitive cell has precluded any previous full electronic
structure study. Using an efficient, local orbital based method within the
local spin density approximation to study the electronic structure, we find a
gap between a bonding valence band complex and an antibonding conduction band
continuum. The bonding bands lack one electron per formula unit of being
filled, making them low carrier density p-type metals. The hole resides in the
MnBi4 tetrahedral unit and partially compensates the high spin d^5 Mn moment,
leaving a net spin near 4 \mu_B that is consistent with experiment. These
manganites are composed of two disjoint but interpenetrating `jungle gym'
networks of spin 4/2 MnBi4^{9-} units with ferromagnetic interactions within
the same network, and weaker couplings between the networks whose sign and
magnitude is sensitive to materials parameters. Ca14MnBi11 is calculated to be
ferromagnetic as observed, while for Ba14MnBi11 (which is antiferromagnetic)
the ferro- and antiferromagnetic states are calculated to be essentially
degenerate. The band structure of the ferromagnetic states is very close to
half metallic.Comment: 17 pages, containing 10 postscript figures and 5 tables. Two
additional figures (Fig.8 and 11 of the paper) are provided in JPG format in
separate files. Submitted to Phys. Rev. B on September 20th 200
The Shifting Imaginaries of Corporate Crime
This article begins by setting out an analysis of the process of conventionalizing corporate crime that arises from the symbiotic relationship between states and corporations. Noting briefly the empirical characteristics of four broad categories of corporate crime and harm, the article then turns to explore the role of the state in its production and reproduction. We then problematize the role of the state in the reproduction of corporate crime at the level of the global economy, through the “crimes of globalization” and “ecocide,” warning of the tendency in the research literature to oversimplify the role of states and of international organizations. The article finishes by arguing that, as critical academics, it is our role to ensure that corporate crime is never normalized and fully conventionalized in advanced capitalist societies
Specific Heat Discontinuity, deltaC, at Tc in BaFe2(As0.7P0.3)2 - Consistent with Unconventional Superconductivity
We report the specific heat discontinuity, deltaC/Tc, at Tc = 28.2 K of a
collage of single crystals of BaFe2(As0.7P0.3)2 and compare the measured value
of 38.5 mJ/molK**2 with other iron pnictide and iron chalcogenide (FePn/Ch)
superconductors. This value agrees well with the trend established by Bud'ko,
Ni and Canfield who found that deltaC/Tc ~ a*Tc**2 for 14 examples of doped
Ba1-xKxFe2As2 and BaFe2-xTMxAs2, where the transition metal TM=Co and Ni. We
extend their analysis to include all the FePn/Ch superconductors for which
deltaC/Tc is currently known and find deltaC/Tc ~ a*Tc**1.9 and a=0.083
mJ/molK**4. A comparison with the elemental superconductors with Tc>1 K and
with A-15 superconductors shows that, contrary to the FePn/Ch superconductors,
electron-phonon-coupled conventional superconductors exhibit a significantly
different dependence of deltaC on Tc, namely deltaC/Tc ~ Tc**0.9. However
deltaC/gamma*Tc appears to be comparable in all three classes (FePn/Ch,
elemental and A-15) of superconductors with, e. g., deltaC/gamma*Tc=2.4 for
BaFe2(As0.7P0.3)2. A discussion of the possible implications of these
phenomenological comparisons for the unconventional superconductivity believed
to exist in the FePn/Ch is given.Comment: some disagreement in reference and footnote numbering with the
published versio
Chemical Bonding in Solids
This chapter discusses the various classes of hydride compounds, with a special focus on saline and metallic hydrides as well as oxyhydrides. It includes the following topics: thermodynamic stability, crystal chemistry, synthesis, and physical properties. The chapter also highlights recent progress in understanding hydride ion mobility in alkaline earth hydrides. It further deals with hydride compounds and in particular those containing alkali, alkaline earth, and transition and rare earth metals. The saline hydrides, that is, AH and AeH2 (with A=Li, Na, K, Rb, and Cs; Ae=Mg, Ca, Sr, and Ba) are proper ionic materials, in which hydrogen is present as hydride anions, H−. Saline hydrides show many similarities with their halide analogues, especially concerning crystal and electronic structures and, perhaps to a lesser extent, physical attributes such as brittleness, hardness, and optical properties
Roadmap on energy harvesting materials
Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere
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