PhD subjects

10 sujets INAC

Dernière mise à jour : 19-01-2018


««

• Solid state physics, surfaces and interfaces

 

Manipulation of spin currents and magnetic state at the nanoscale using the spin orbit coupling

SL-DRF-18-0058

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

Spintronique et technologie des composants (SPINTEC)

Laboratoire Spintec (SPINTEC)

Grenoble

Contact :

Laurent VILA

Jean Philippe ATTANE

Starting date : 01-10-2018

Contact :

Laurent VILA

CEA - DSM/INAC/SP2M/NM

0438780355

Thesis supervisor :

Jean Philippe ATTANE

Universite Joseph Fourier - INAC/SP2M

0438784326

Personal web page : http://inac.cea.fr/Pisp/laurent.vila/

Laboratory link : http://www.spintec.fr/research/spin-orbitronics/

The development of spin electronics, or spintronics, allows to imagine many devices taking advantage of an electronics no longer based solely on the electrical charge of the carriers but also on their spin. This new degree of freedom offers additional means of conveying information, and introduces new ways to manipulating it.

Very recently, a collection of Spin Orbit based spin- to-charge interconversion mechanisms (Spin Hall effects, Rashba and Topological Insulators) were observed experimentally. It appears in the set of non-magnetic metals, semiconductors or oxydes, and sorts the carriers according to their spin state. It allows injecting and detecting spins without necessarily using magnetic materials or a magnetic field, which is both conceptually and technologically very interesting.

In this framework, we wish to create lateral nanostructures taking advantage of pure spin current generated by harnessing the Spin Orbit coupling for both spin to charge interconversion mechanisms and the manipulation of magnetization state of nano-object (dot or magnetic domain wall) by absorption of this current and spin transfer torque. Material of interest will be metals, oxydes and topological insulators to generate or detect spin currents, and will be applied to the manipulation of the magnetic state of a nanoelement, an example of a recent realization being given on the figure.

If subjects related to the spin transfer by absorption of a pure spin current are very competitive, they are scientifically rich, and currently booming. This area of research is still largely open to exploration, and we are benefiting from our recent development of efficient injection and detection devices.

The proposed topic lies in basic research but with a clear opening towards applied research. The trainee will benefit from the technical and scientific environment of the laboratory, and the collaborations put in place with the major actors of the field at the international level. This project is supported by funding from the ANR.

Antiferromagnetic spintronics

SL-DRF-18-0274

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

Spintronique et technologie des composants (SPINTEC)

Laboratoire Spintec (SPINTEC)

Grenoble

Contact :

Vincent BALTZ

Starting date : 01-10-2018

Contact :

Vincent BALTZ

CNRS - DFR/INAC/SPINTEC/SPINTEC

04 38 78 03 24

Thesis supervisor :

Vincent BALTZ

CNRS - DFR/INAC/SPINTEC/SPINTEC

04 38 78 03 24

Laboratory link : http://www.spintec.fr/research/antiferromagnetic-spintronics/

More : https://arxiv.org/ftp/arxiv/papers/1606/1606.04284.pdf

Antiferromagnetic materials (antiparallel alignment of the atomic magnetic moments) could represent the future of spintronic applications thanks to the numerous interesting features they combine: they are robust against perturbation due to magnetic fields, produce no stray fields, display ultrafast dynamics and are capable of generating large magneto-transport effects. Intense research efforts are being invested in unraveling spin-dependent transport properties in antiferromagnetic materials. Whether spin-dependent transport can be used to drive the antiferromagnetic order and how subsequent variations can be detected are some of the thrilling challenges to address.

The nature of the elements constituting the antiferromagnetic material and the quality of the interfaces will be the adjustable parameters. We will consider mainly the efficiency of spin injection and the interfacial filtering, the absorption of spins in the core of the material and the absorption characteristics lengths, the order temperatures and the magnetic susceptibility, and the efficiency of the spin-orbit coupling via the spin Hall effect.

This PhD thesis work is experimental. It will build on the many techniques of fabrication (sputtering, molecular beam epitaxy, clean room nanofabrication) and characterization (magnetometry, ferromagnetic resonance, transport) at SPINTEC and benefit from the collaboration with our partner laboratories for experiments with a resonant cavity and for access to complementary materials.

Theoretical investigation of finite-temperature spin dynamics

SL-DRF-18-0324

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

Photonique, Electronique et Ingénierie Quantiques (PHELIQS)

Groupe Théorie (GT)

Grenoble

Contact :

Mike ZHITOMIRSKY

Starting date : 01-10-2018

Contact :

Mike ZHITOMIRSKY

CEA - DRF/INAC/PHELIQS/GT

04.38.78.43.30

Thesis supervisor :

Mike ZHITOMIRSKY

CEA - DRF/INAC/PHELIQS/GT

04.38.78.43.30

Computer simulations play an increasingly important role in our exploration of Nature. The Monte Carlo modeling of spin systems is one of the true success stories of the computer-aided theoretical studies. At the same time, numerical and analytical investigation of the dynamic properties of magnetic systems is far less mature with the majority of theoretical works employing the phenomenological Landau-Lifshitz-Gilbert equations.

This PhD project is focused on an alternative microscopic approach based on the material-specific spin Hamiltonians that describe interactions between atomic magnetic moments. The numerical spin dynamics computations in real time have to be combined with the thermal Monte Carlo calculations. This will allow to model magnetic materials at an arbitrary temperature above and below the possible magnetic transitions. The obtained results will be of direct relevance to a wide range of experimental studies performed on neutron and synchrotron facilities as well as to the field of spintronics and nanomagnetism.

Miniature and ultra-sensitive magnetometer for space missions

SL-DRF-18-0141

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

Spintronique et technologie des composants (SPINTEC)

Laboratoire Spintec (SPINTEC)

Grenoble

Contact :

Hélène BEA

Claire BARADUC

Starting date : 01-10-2018

Contact :

Hélène BEA

UGA - DRF/INAC/SPINTEC/SPINTEC

04 38 78 08 46

Thesis supervisor :

Claire BARADUC

CEA - DRF/INAC/SPINTEC/SPINTEC

04 38 78 42 35

Laboratory link : http://www.spintec.fr/research/magnetic-sensors/

The aim is to develop a miniature and ultra-sensitive magnetometer (100 fT / Hz^1/2), using magnetic tunnel junctions and microfabrication techniques from microelectronics. This magnetometer could replace the magnetometers currently used on space missions with a mass reduction by a factor of 100. This extreme lightness (~ 1 g without electronics) would represent a competitive advantage over inductive sensors currently used in space missions (mass > 1 kg).

The proposed magnetometer combines a magnetic tunnel junction as sensing element of the sensor, a flux concentrator to amplify the field to be measured, and a magnetic field modulation system to reduce the noise of the measurement. Preliminary studies have shown the feasibility of the basic bricks of this sensor. It is now necessary to optimize the flux concentrator and the magnetic tunnel junction, in particular by developing an innovative junction that is currently the subject of a patent application.

The thesis work will mainly be experimental (microfabrication, electrical and magnetic characterization, noise measurements, magnetic imaging) but will also include analysis and micromagnetic simulations.

High-resolution TEM magnetic imaging of nanotubes for spintronics

SL-DRF-18-0518

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

Spintronique et technologie des composants (SPINTEC)

Laboratoire Spintec (SPINTEC)

Grenoble

Contact :

Eric GAUTIER

Jean-Luc ROUVIERE

Starting date : 01-09-2018

Contact :

Eric GAUTIER

CNRS - DRF/INAC/SPINTEC/SPINTEC

0438784226

Thesis supervisor :

Jean-Luc ROUVIERE

CEA - DSM/INAC/SP2M/LEMMA

04 38 78 50 86

Personal web page : https://cv.archives-ouvertes.fr/olivier-fruchart

Laboratory link : http://www.spintec.fr/research/spin-textures/

More : http://fruchart.eu

The objective of the internship is the study by transmission electron microscopy (TEM) of magnetic nanotubes chemically synthesized. We are studying these as model objects to explore the concept of information storage in a 3D magnetic medium, based on the propagation of magnetic walls along one-dimensional structures. Physico-chemical study of the material and magnetic imaging at the nanometer scale will be used to explore and understand the arrangement of domains and domain walls in these systems, whose synthesis has been achieved recently.

The experimental techniques that will be used will be chemical and structural analysis by electron diffraction and high-resolution imaging, magnetic imaging and electron holography, in a transmission electron microscope. The student will perform sample preparation for electron microscopy, the installation of a device for an observation in the microscope, and imaging.

Microscopy will be conducted in close collaboration with INAC-MEM-LEMMA a,d LETI. The work also includes an aspect of processing, interpretation of data and participation in micro-magnetic simulations to assist physical understanding. These will be done in collaboration with the laboratory of simulation group SPINTEC / NEEL.

Theoretical study of advanced magnetocaloric materials

SL-DRF-18-0177

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

Photonique, Electronique et Ingénierie Quantiques (PHELIQS)

Groupe Théorie (GT)

Grenoble

Contact :

Mike ZHITOMIRSKY

Starting date : 01-10-2018

Contact :

Mike ZHITOMIRSKY

CEA - DRF/INAC/PHELIQS/GT

04.38.78.43.30

Thesis supervisor :

Mike ZHITOMIRSKY

CEA - DRF/INAC/PHELIQS/GT

04.38.78.43.30

Laboratory link : http://inac.cea.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=1157

An external magnetic field affects the entropy of a magnetic system and provokes temperature variations which can be used for magnetic refrigeration. Such an alternative cooling technology is increasingly important nowadays for space telescopes, particle physics experiments and quantum computing. The existing adiabatic demagnetization refrigerators utilize paramagnetic salts, which have limited capacity for temperatures above 1 K. Recently, two new families of magnetocaloric materials suitable for applications in the 1-4 K temperature range have been proposed: geometrically frustrated spin systems and dipolar magnets. We plan to study the magnetocaloric properties of such materials using large scale Monte Carlo simulations of realistic spin models appropriate for the known, Gd3Ga5O12 and GdLiF4, as well as for the prospective, Yb2Ti2O7 and Yb3Ga5O12, magnetocaloric materials. The theoretical study will benefit from a collaboration with the on-going experimental work at INAC.

Formation and stabilization of size-controlled graphene nanopores for gas filtration application

SL-DRF-18-0519

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

Modélisation et Exploration des Matériaux (MEM)

Laboratoire d'Etude des Matériaux par Microscopie Avancée (LEMMA)

Grenoble

Contact :

Hanako OKUNO

Gilles CUNGE

Starting date : 01-10-2018

Contact :

Hanako OKUNO

CEA - DRF/INAC/MEM/LEMMA

04 38 78 20 73

Thesis supervisor :

Gilles CUNGE

CNRS - CNRS/LTM

0438782408

The introduction of nanoscale pores in graphene has attracted much attention for a large variety of applications that involve water purification, gas filtration, chemical separation, and DNA sequencing. Graphene has been proposed as an effective separation membrane. Removing carbon atoms to form size-controlled nanopores, size-selective separation membrane might be possible based on the molecular sieving effects.

In this Thesis project, we aim at studying formation mechanism and edge natures of sub-nanometer size nanopores in graphene for gas filtration membrane application. The final objective is to realize size-controlled stable nanopores in graphene monolayers using plasma technology and to integrate the developed nanopore formation process into gas filtration membrane technology to test their selectivity especially on hydrogen separation.

SL-DRF-18-0072

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

Photonique, Electronique et Ingénierie Quantiques (PHELIQS)

Laboratoire Silicium Nanoélectronique Photonique et Structures (SINAPS)

Grenoble

Contact :

Emmanuel PICARD

Pierre R. MARCOUX

Starting date : 01-09-2018

Contact :

Emmanuel PICARD

CEA - DRF/INAC/PHELIQS/SINAPS

04 38 78 90 97

Thesis supervisor :

Pierre R. MARCOUX

CEA - DRT/DTBS/SBSC/LCMI

04 38 78 15 04

Advanced AlGaN-based 1D nanostructure growth for UV emission

SL-DRF-18-0392

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

Photonique, Electronique et Ingénierie Quantiques (PHELIQS)

Laboratoire de Nano Physique des Semi-Conducteurs (NPSC)

Grenoble

Contact :

Christophe DURAND

Joël EYMERY

Starting date : 01-10-2018

Contact :

Christophe DURAND

UGA - DRF/INAC/PHELIQS/NPSC

04 38 78 19 77

Thesis supervisor :

Joël EYMERY

CEA - DRF/INAC/MEM/NRS

04 38 78 30 15

The growth of GaN nanowires surrounded by GaN/InGaN quantum wells grown by MOVPE (Metal-Organic Vapor Phase Epitaxy) has been studied extensively in the laboratory and is now well mastered [1]. This is an important step forward as it makes possible the manufacturing and industrial production of nanowire-based LEDs for the emission of visible light (blue, green and white).

In the same way, we wish to develop new 1D nanostructures for the emission of UV light. Pioneering and promising results have been obtained in the laboratory using GaN/InAlN quantum wells grown around the GaN wires exhibiting emission at 330 nm up to room temperature [2]. By applied a in situ annealing, we have demonstrated the possibility of etching the GaN wires core, while preserving the optical properties of the quantum wells. Thus, we made for the first time quantum well-based tubes with excellent optical properties [3].

The aim of the thesis is to develop new quantum wells, such as GaN/AlGaN or AlGaN/AlN grown on 1D nanostructures (wires, tubes, bands, etc.), in order to be able to reach far UV emission wavelengths (<280 nm) with the possibility destroying bacteria. This is a major challenge for the development of UV LEDs considering new applications such as water treatment or sterilization. The purpose of this study is to better understand the potentiality of 1D nanostructures to emit far UV. This type of quantum well grown on 1D nanostructures also makes possible the realization of IR subband detectors in the THz domain.

The development of several stages will be necessary to carry out this thesis project: (i) the realization of 1D nanostructures in Al(Ga)N by combining growth and selective etching, (ii) epitaxy of AlGaN-based quantum wells grown on these nanostructures, (iii) advanced structural and optical characterization, and (iv) the design of new devices and their favrication. The thesis will be based on a collaborator network (C2N, EPFL, Univ. Tyndall ...) in order to progress effectively.

The work is essentially experimental to explore fundamental phenomena at the nanometer scale while participating in a active research topic on the development of new LED devices for UV emission.



[1] R. Koester et al., Nano Lett. 11, 4839 (2011).

[2] C. Durand et al., ACS Photonics 1, 38 (2014).

[3] C. Durand et al., Nano Lett. 17, 3347 (2017).



Study of physical properties of magnetic skyrmions for sensing applications

SL-DRF-18-0215

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

Spintronique et technologie des composants (SPINTEC)

Laboratoire Spintec (SPINTEC)

Grenoble

Contact :

Claire BARADUC

Hélène BEA

Starting date : 01-09-2018

Contact :

Claire BARADUC

CEA - DRF/INAC/SPINTEC/SPINTEC

04 38 78 42 35

Thesis supervisor :

Hélène BEA

UGA - DRF/INAC/SPINTEC/SPINTEC

04 38 78 08 46

Laboratory link : http://www.spintec.fr/research/magnetic-sensors/

Skyrmions are chiral magnetic bubbles: magnetization follows a cycloid along a line across the skyrmion. They can appear in heavy metal/ferromagnet/oxide ultrathin trilayers. Such texture results from the presence of an interfacial interaction called Dzyaloskinskii-Moriya interaction. It makes the skyrmions stable, less sensitive to defects as compared to usual domain walls and easily moveable by electrical current. They are currently very popular as they could be used as dense storage nanoscale data bits, or for magnetic logic.

Their size may be modified by a magnetic field. Moreover, using magneto-optical microscopy, we have recently shown that a gate voltage can modulate the size and density of magnetic skyrmions in ultrathin films, ultimately leading to the realization of a skyrmion switch [1]. This new degree of freedom may thus allow to create multifunctional spintronic devices or to better control the skyrmion properties.



In order to develop skyrmion based spintronic devices, the objectives of this thesis would be:

-to better understand and control the different contributions in the Dzyaloshinskii-Moriya interaction by playing on the materials thanks to a support from theoreticians at Spintec.

- to optimize the tunability of skyrmion properties with the gate voltage by performing a material study. Skyrmion behavior with temperature will also be studied as a device should operate in the -40 to 100°C range for applications.

-to characterize the electrical signature of skyrmions by using magneto-optical microscopy coupled with magnetotransport. This electrical signal is necessary to read the state of a skyrmion-based device but is still a technological challenge, the signals being usually quite small.

- finally, to assess the potential for skyrmions to be used in spintronic devices.



[1] M. Schott et al. Nano Lett., 17, 3006 (2017)

 

Retour en haut