Description of the thesis topic

Spintronic exploits spin in addition to the charge of current carriers. It is born from the discovery of giant magnetoresistance in metallic multi-layers and enables numerous applications in the field of memories and magnetic sensors for example. This major breakthrough in electronics was awarded with a Nobel Prize of physics in 2007. Traditionally, spintronic relies on ferromagnetic metals such as Ni or Co as generators and detectors of spin currents. Nevertheless, ferromagnetic metals have several drawbacks: (i) they can generate undesired local magnetic fields hindering the densification of devices and (ii) a large voltage is required for reversing their magnetization, hence incompatible with our quest for low energy consumption devices. A new direction of spintronic exploits the spin-orbit interaction of non-magnetic materials, called spin-orbitronics, and allows to reduce the energy cost of such devices. However, functionalities such as data storage are lost with this type of devices.

In the quest of low energy consumption devices, the use of ferroelectric materials appears to be a very promising pathway toward efficient materials: the reversal of spontaneous polarization represents a lower energy cost than the reversal of magnetization. The next step consists of coupling ferroelectricity with magnetic and electronic properties: this can be achieved (i) in multiferroic materials combining ferroelectric and magnetic orders or (ii) in non-magnetic materials presenting a sizable spin-orbit interaction and in which the amplitude and orientation of the spontaneous polarization enables a non-volatile control of the spin textures. The coupling of ferroelectricity with the electronic and magnetic properties of materials appears to be a strong lever for designing energy-efficient materials able to respond to current climate problems.


The aim of the thesis is to produce ferroelectricity in magnetic materials and/or in materials possessing a strong spin-orbit interaction in order to design compounds (i) combining ferroelectricity and magnetism and (ii) showing optimal properties. To that end, the highly multifunctional character of perovskite oxides, among which the most popular ferroelectrics like BaTiO3 and many magnetic materials belong, will be harnessed. These studies will be performed with Density Functional Theory (DFT) simulations allowing to resolve the electronic problem in matter and to reliably model the properties of materials.

Activities:
- Materials modelling
- Lattice mode couplings
- Data analysis
- Extract physical trends and rules
- Make hypothesis and perform numerical checks

A motivated candidate is expected (i) to carry out this important topic and (ii) to work in collaboration with the various researchers from the lab involved in this project. The candidate must possess a Research Master's degree in Solid State Physics or Materials Science or hold an engineering title in these fields. The candidate must have a strong background in condensed matter physics and be familiar with numerical simulations and crystallography. Skills about solving the electronic problem in materials (DFT) is strongly welcome, as well as familiarity with the Linux world.

Work Context

The CRISMAT laboratory is a joint CNRS, ENSICAEN and Normandy University research unit located in Caen and entailing a hundred of researchers and engineers. It is a laboratory internationally recognized for its expertise on oxide materials. The PhD student will become a member of the Thin Films, Interfaces and Surfaces group at CRISMAT and will be supervised by Julien Varignon, Lecturer at ENSICAEN and theoretician. The PhD student will enjoy a favorable environment to carry out the missions with access to numerous techniques and tools locally. This project is part of the PEPR-SPIN framework and the PhD will benefit of strong interactions with the different French groups involved in this project.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.