The Oxitronics team is part of the CNRS/Thales laboratory located within Thales Research and Technology in Palaiseau, France. Our main scientific interests are in oxide electronics, spintronics, multiferroics, ferroelectrics and oxide interfaces. This website contains information on our past and current research, our group members and our publications. See also our events page for information on workshops, schools, etc.
Rare-earth titanates are Mott insulators, and emerge as promising building blocks to realize exotic electronic states at oxide interfaces. For small rare-earths such as Dy, these titanates are canted ferrimagnets. However, critical to this magnetic order is the 3+ valence of the Ti cations, which is hard to stabilize. In our recent paper just published in Advanced Materials, we report for the first time the growth of high-quality DyTiO3 thin films, with excellent, bulk-like magnetic properties at high thickness, and a surprisingly enhanced saturation magnetization at low thickness. This thickness dependence of the magnetic properties is reminiscent of dead-layer effects in more conventional materials in which magnetization is reduced at low thickness. Through a combination of X-ray spectroscopies and magnetometry we have shown that this “living-dead” magnetic layer arise from uncoupled, paramagnetic Dy ions with neighbouring non-magnetic Ti4+ present at the film surface.
This work was performed in collaboration with the Helmholtz-Zentrum Berlin, the University of Würzburg and the Paul-Scherrer Institute.
A Living-Dead Magnetic Layer at the Surface of Ferrimagnetic DyTiO3 Thin Films
R. Aeschlimann et al ; Adv. Mater. 10.1002/adma.201707489 (2018)
Through a combination of conductive-tip atomic force microscopy (CAFM) and X-ray photemission electron microscopy (XPEEM), we have investigated the phase separation ocurring at the metal-insulator transition of NdNiO3 thin films. Our images reveal the nucleation of ∼100–300 nm metallic domains in the insulating state that grow and percolate as temperature increases. In our paper just out in Nano Letters, we discuss the resistance contrast mechanism, analyze the microscopy and transport data within a percolation model, and propose experiments to harness this mesoscopic electronic texture in devices.
This work was performed in collaboration with the Helmholtz-Zentrum Berlin and the Laboratoire de Physiques des Solides in Orsay.
Direct Mapping of Phase Separation across the Metal–Insulator Transition of NdNiO3
D. Preziosi et al ; Nano Lett. 10.1021/acs.nanolett.7b04728 (2018)
If you wonder how we perform our experiments and want to delve into the process of growing our oxide samples, you can have a look at this video published as a an article in JOVE, the Journal Of Visualized Experiments. It shows our group member Diogo Vaz growing an heterostructure combining an oxide grown by pulsed laser deposition and a metal deposited by sputtering. The sample is characterized by in-situ X-ray photoelectron spectroscopy to probe the formation of a 2-dimensional electron gas in SrTiO3, and characterized by magnetotransport. The manuscript is available in pdf here.
Growth and electrostatic/chemical phroperties of metal/LaAlO3/SrTiO3 eterostructures
D.C Vaz et al ; J. Vis. Exp. 132, e56951, doi:10.3791/56951 (2018).
Along with Dutch chemist Daniël Vanmaekelbergh our group member Manuel Bibes will receive the Descartes-Huygens Prize 2017. That was announced today by the Royal Netherlands Academy of Arts and Sciences (KNAW), the Embassy of France in the Netherlands and the Académie des Sciences. The two nanoscientists have been awarded the prize for their outstanding research and their contribution to Franco-Dutch relations. Manuel will use his Descartes-Huygens Prize to spend three months conducting research at the Center for Cognitive Systems and Materials at the University Groningen. He will also visit the nanolaboratories at the University of Twente. The three organisations aim to combine their expertise to develop low-power electronics.
Pictures from the Award Ceremony that took place on February 20, 2018 at the Académie des Sciences in Paris.
As the old adage goes, Seeing is believing! This is particularly acute for antiferromagnets that despite their interest for low-power, ultrafast spintronics applications remain practically impossible to image at the nanoscale since their the antiparallel order of neighbouring spins results in a vanishing magnetization. Usually, reciprocal-space, bulk averaging methods such as neutron diffraction are the techniques of choice to characterize antiferromagnets, but then microscopic details remain concealed. In our recent paper just published in Nature, we report the first real-space imaging of long-range periodic order in a complex antiferromagnet, bismuth ferrite (BiFeO3). We have used a new technique exploiting the extreme magnetic sensitivity of the photoluminescence response of a single nitrogen-vacancy (NV) center located near the apex of an atomic force microscope tip. In addition, we have also taken advantage of the magnetoelectric coupling present in BiFeO3 to evidence the electrical control of the cycloid propagation direction in real space. Besides highlighting the potential of NV magnetometry for imaging complex antiferromagnetic orders at the nanoscale, our results demonstrate how BiFeO3 can be used in the design of reconfigurable nanoscale spin textures on-demand.
This work was performed in collaboration with Lab. Charles Coulomb, CEA-Saclay, C2N, Synchrotron SOLEIL, Lab. Aimé Cotton and University of Basel. Left image on figure courtesy of P. Maletinsky.
Real-space imaging of non-collinear antiferromagnetic order with a single-spin magnetometer
I. Gross et al ; Nature 459, 252 (2017)
Our group member Agnès Barthélémy has just been awarded the Lazare-Carnot Prize of the French Academy of Science. This Prize created by the French Ministry of Defence acknowledges important advances in fundamental research with perspectives of civilian or military applications. Congratulations Agnès !
On July 13, 2017, Vincent Garcia defended his Habilitation Thesis in Palaiseau. He presented his ~10 year work on ferroelectric tunnel junctions, from their physical principle of operation through their combination with spintronics to their use as memristors. He also gave perspectives and proposed future directions of research. Lots of exciting new concepts to explore. Well done, Vincent !