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PhD subjects

Dernière mise à jour : 16-10-2017

2 sujets IRAMIS

• Solid state physics, surfaces and interfaces

• Ultra-divided matter, Physical sciences for materials

 

Theoretical investigation of the magnetic anistropy of hybrid systems for molecular spintronics

SL-DRF-18-0045

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Cyrille BARRETEAU

Starting date : 01-12-2017

Contact :

Cyrille BARRETEAU

CEA - DRF/IRAMIS/SPEC/GMT

+33(0)1 69 08 38 56

Thesis supervisor :

Cyrille BARRETEAU

CEA - DRF/IRAMIS/SPEC/GMT

+33(0)1 69 08 38 56

Personal web page : http://iramis.cea.fr/Pisp/cyrille.barreteau/

Laboratory link : http://iramis.cea.fr/spec/GMT/

Nanomagnetism is an active field at the frontier of various domains. It consists in the study (and use) of the magnetism of nanometer sized systems. Magnetic properties of nano-objects generally strongly differ from their bulk counterpart. A major issue is to control/manipulate their magnetic properties. One of the fundamental properties of magnetic materials is their magnetic anisotropy which is characterized by their easy axis but also anisotropic magnetoresistance (AMR). It has been recently demonstrated that the interaction between a magnetic thin film and adsorbed molecules can greatly modify the anisotropy of the film due to hybridization between the molecule and the surface atoms of the substrate. Recent experiments have also shown that large AMR can be achieved in “simple” systems such as nano-conctrictions of nickel connected via a benzene molecule.

In this internship we propose to study via electronic structure methods (ab-initio and/or tight-binding) the magnetic anisotropy of few simple systems. We will first consider cobalt and iron thin films in interaction with simple molecules. More complex systems will be further investigated. The final goal is to find systems molecule/substrate with optimal properties in view of possible applications.

Intermediate amorphous states during precipitation of cerium oxalate: towards a new nucleation model

SL-DRF-18-0111

Research field : Ultra-divided matter, Physical sciences for materials
Location :

Service Nanosciences et Innovation pour les Materiaux, la Biomédecine et l'Energie (NIMBE)

Laboratoire Interdisciplinaire sur l'Organisation Nanométrique et Supramoléculaire (LIONS)

Saclay

Contact :

Sophie CHARTON

David CARRIÈRE

Starting date : 01-11-2018

Contact :

Sophie CHARTON

CEA - DEN/DTEC/SGCS

+33 (0)4.66.79.62.29

Thesis supervisor :

David CARRIÈRE

CEA - DSM/IRAMIS/NIMBE

0169085489

Personal web page : http://iramis.cea.fr/Pisp/68/david.carriere.html

Laboratory link : http://iramis.cea.fr/nimbe/lions/index.php

The formation of crystals by liquid reaction takes place in the many natural and artificial processes, and in particular in reactive crystallization processes. The control of the kinetics of the formation, the size and the morphology of the precipitates is still very challenging. Size control of precipitated powder is also an important issue of nuclear fuel treatment, where plutonium is precipitated as oxalate, before being converted into the oxide used in the manufacture of MOX.

The reference theory for predicting rate of crystal formation, used in process modeling, is the classical theory of nucleation (CNT), which is based on the thermodynamic description of the liquid-vapor equilibrium proposed by Gibbs in 1876. But this model sometimes dramatically fails because it ignores all the disordered intermediate states possibly achieved between the initial solution and the final crystal: clusters, liquid-liquid phase separations, amorphous particles or networks, etc. In particular, such amorphous intermediate states were observed in the precipitation of cerium oxalate, one of the reference simulating systems for plutonium, suggesting a two-stage nucleation process in contradiction with the CNT.

The general objective of this thesis is to characterize the intermediate states of the nucleation of cerium oxalate and their impact on the predictions of classical theory. As a close collaboration between CEA Marcoule and CEA Saclay, this thesis will combine techniques known to be able to tackle this difficult problem: X-ray scattering in laboratory and synchrotron facilities (SAXS/WAXS), microfluidics, thermodynamic and kinetic models.

 

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