Our latest experimental results and calculations prove that the paramagnetism of gold nanoparticles is of orbital nature and results from the conduction electrons being driven into persistent currents by external magnetic fields. Moreover, when the nanoparticles are organized in a regular 3D lattice the persistent currents become self-sustained, therefore yielding ferromagnetism. Up to a nanoparticle size of ca. 20nm, the magnetization easily persists above room temperature. On the basis of these observations, we believe that a vast majority of conductive nanoparticle could develop a magnetic moment because of persistent currents. Unconventional magnetic materials could consequently be made from self-assembled functionalized nanoparticles, with no or reduced use of 3f or 4f elements, which is unprecedented.
We propose this innovative and unconventional project which aims at fully understanding this persistent currents phenomenon and at synthesizing totally innovating magnetic materials. Our strategy will open new routes in the field of magnetism, information storage and processing :
1 - there is today no magnetic material made from the self-assembly of nanometric building blocks making no use of magnetic elements (3d or 4f). Our approach is unprecedented and based on a new paradigm.
2 - we have preliminary data showing that 3D liquid-crystalline networks of non-magnetic nanoparticles (Au, Ag) are para or ferromagnetic above room temperature. The concept can be extended to non-noble metals. The combination of chemists, physicists as well as theoreticians is an asset to the success of this program.
3 - On the economical side, one may immediately think of many applications for such materials, including new lightweight paramagnetic materials with high saturation and low losses, new ferromagnetic materials made without use of rare earth elements, electrically or optically addressable magnets and optical metamaterials.
Development of advanced magnetic materials without or with reduced use of critical raw materials is currently hotly investigated (cf. EU H2020 FET work programme).
The periodic modulation of dielectric permittivity and magnetic permeability which will naturally arise in such materials make them excellent candidates for the development of metamaterials, with breakthrough applications in the fields of optics or communication.
Understanding the persistence of quantum effects in nanometric structures up to room temperature will open impressive prospects in the field of quantum computing.
4 - The task force involved in this project gathers scientists having expertise in synthetic chemistry, self-assembling materials, near field studies and molecular magnetism. Strong interactions are already ongoing with mesoscopic theoretical physicists lead by R.A. Jalabert, who has published reference papers in the field of orbital magnetism. This project will also directly benefit from the work of G. Weick (ANR JCJC Q-METAMAT) which program encompasses a great part of the underlying theoretical physics. The success of this project will therefore be the result of the synergetic collaboration of several scientists, all part of the same institute. Each of the PIs involved has a proven record of original papers in high-impact journal and a proven expertise as coordinator/partner of scientific projects.
Monsieur donnio bertrand (CNRS DR ALSACE)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IPCMS (CNRS/UDS) CNRS DR ALSACE
Help of the ANR 421,824 euros
Beginning and duration of the scientific project: December 2015 - 48 Months