The HYPNOSE project proposes to follow a new path in magnetization manipulation by combining the development of hybrid systems and optical magnetization control. Our approach is based on the development of vertically self-assembled nanocomposites consisting of epitaxial magnetic nano-pillars in photostrictive thin films. These systems, which couple magnetism and photostriction, will be used to control magnetization by light. Our approach includes the study of dynamic aspects of magnetization manipulation down to ultra-short time scales. The consortium brings together teams with state-of-the-art expertise and experimental facilities to cover all aspects of a project addressing the production of complex, functional, self-assembled nano-objects, in which the nanoscale plays a key role for magnetization control and ultra-fast response.
Initially, different material couples will be investigated in order to obtain vertically self-assembled nanocomposites featuring a strong coupling of the photostrictive properties of the matrix and the magnetic properties of the nano-pillars. Photo-induced deformation of the matrix, combined with epitaxy of the nano-pillars, will induce changes in magneto-elastic anisotropy. The systems will be grown by pulsed laser ablation. Growth parameters will be adjusted to control the size, density, epitaxy and axial deformation of the nano-pillars in the matrix. Following this optimization phase, two types of more complex systems will be developed: exchange spring-type systems and systems adapted to promote photo-induced reorientation of out-of-plane/in-plane magnetization. The photostrictive and magnetic properties of the systems will be measured using a range of complementary techniques (diffraction, magnetometry and magneto-optics).
Fig. 1: (a) Illustration of the photostrictive effect. (b) Schematics of a VAN with nanopillars of material A embedded in a thin film of material B.
Then, the dynamic response of the systems to pulsed laser excitation will be studied in detail. The implementation of a set of state-of-the-art pump-probe techniques will enable us to probe the ultrafast dynamics of the various degrees of freedom. Magnetization dynamics will be studied using a combination of magneto-optical time-resolved Kerr effect and time-resolved magnetic resonant X-ray scattering (Tr-XRMS). Together, these experiments will enable us to describe the dynamic processes at work in photostrictive-magnetic nanocomposites and optimize their response time. The same type of techniques will be used to study the response of exchange spring systems and systems designed for photo-induced out-of-plane/in-plane reorientation of magnetization.
Finally, a technique for transferring nanocomposites onto membranes will be developed as part of this project, enabling time-resolved coherent imaging experiments in transmission. This will pave the way for studying the dynamics of single nanopillars.
