Explaining the magnetic moment reduction of Fullerene encapsulated Gadolinium through a theoretical model

We propose a Theoretical model accounting for the recently observed reduced magnetic moment of Gadolinium in fullerenes. While this reduction has been observed also for other trivalent rare-hearth atoms (Dy3+, Er3+, Ho3+) in fullerenes and can be ascribed to crystal field effects, the explanation of this phenomena for Gd3+ is not straightforward due to the sphericity of its ground state (S=7/2, L=0). In our model the momentum lowering is the result of a subtle interplay between hybridisation and spin-orbit interaction

Observation and theoretical description of the pure Fano-effect in the valence-band photo-emission of ferromagnets

The pure Fano-effect in angle-integrated valence-band photo-emission of ferromagnets has been observed for the first time. A contribution of the intrinsic spin polarization to the spin polarization of the photo-electrons has been avoided by an appropriate choice of the experimental parameters. The theoretical description of the resulting spectra reveals a complete analogy to the Fano-effect observed before for paramagnetic transition metals. While the theoretical photo-current and spin difference spectra are found in good quantitative agreement with experiment in the case of Fe and Co only a qualitative agreement could be achieved in the case of Ni by calculations on the basis of plain local spin density approximation (LSDA). Agreement with experimental data could be improved in this case in a very substantial way by a treatment of correlation effects on the basis of dynamical mean field theory (DMFT).Comment: 11 pages, 3 figures accepted by PR

Electronic transport, structure, and energetics of endohedral Gd@C82 metallofullerenes

Electronic structure and transport properties of the fullerene C$_{82}$ and the metallofullerene Gd@C$_{82}$ are investigated with density functional theory and the Landauer-Buttiker formalism. The ground state structure of Gd@C$_{82}$ is found to have the Gd atom below the C-C bond on the C$_2$ molecular axis of C$_{82}$. Insertion of Gd into C$_{82}$ deforms the carbon chain in the vicinity of the Gd atoms. Significant overlap of the electron distribution is found between Gd and the C$_{82}$ cage, with the transferred Gd electron density localized mainly on the nearest carbon atoms. This charge localization reduces some of the conducting channels for the transport, causing a reduction in the conductivity of the Gd@C$_{82}$ species relative to the empty C$_{82}$ molecule. The electron transport across the metallofullerene is found to be insensitive to the spin state of the Gd atom.Comment: 13 pages, 7 figures, submitted Nano Let

The reliability of product-specific eco-labels as an agrobiodiversity management instrument

This paper seeks to understand why multinationals prefer to launch a label specific to their own product and examines how reliable these product-specific eco-labels are. A new methodology is applied to assess the extent to which eco-labels live up to claims about their contribution to conservation and the sustainable use of agricultural biodiversity. Product-specific eco-labels are considered as industry self-regulation and all three regulatory stages are studied: the planning, implementation and outcome stage. There are major differences between the product specific eco-labels in the degree in which agrobiodiversity management is part of the normative labeling schemes. Although there are some problems of reliability, such as transparency in the implementation stage and the monitoring in the outcome stage, the degree of reliability of product-specific labels is comparable with eco-labels of international labeling families. The conclusion is that only one of the product-specific eco-labels examined here is reliable when examined in the light of all three stages. The main reason why multinationals establish a product-specific eco-label instead of adopting one from an existing labeling family is that they want to profile themselves as distinct from other companies. The unique character of a product-specific label creates a market opportunity for them

Les dimensions spatiales de la transition énergétique

International audienceEnergy transition is fundamentally acknowledged as a geographical process that happens in particular places, transforms landscape features, produces uneven development and, more generally, entails reconfiguring current spatial patterns of economic and social activities. The way in which spatial processes shape new energy technologies and influence their capacity for transformation, however, has rarely been a focus of analyses. To investigate further the role of space in the energy transition, this chapter proposes to take into account the diffuse materiality of renewable energy resources. Our aim is to contribute to an emerging agenda about the spatialities of energy resources and their political issues at the crossroad of materiality and space. The chapter is divided into four sections. The first briefly presents the field of the geography of energy resources and explains the approach of renewable energy resources as a 'turbulent' materiality. The second proposes theoretical elements inspired by works on the vertical dimension of space to study the processes through which space is configured as a manageable 'volume' for controlling energy material flows. The third examines five case studies from France, Germany and Tunisia. Finally, a discussion about emerging politics of 'volume' in the energy transition aims at providing a critical geographical appraisal of the current development of renewable energie

Quand la transition énergétique est portée par les marchés

International audienceThis chapter offers a critical examination of the conduct of market-based energy transition. Drawing on four case studies from France - tree stumps as conventional fuelwood, non-residential PV production, the development of 'smart home' infrastructure, and the market valuation of residential load shedding - the chapter takes a market studies approach and offers fine-grained accounts of how markets work in practice. Unsurprisingly, the four cases presented here illustrate ways in which markets can lead to positive or negative outcomes in both energy change achievements and participation in steering these changes. They suggest that the potential of markets in relationship to the energy transition depend notably on what the state decides to make of them