arXiv subjects

Laurent Badie

Publications and source records attributed to Laurent Badie.

5 recordsLinked to original sources

arXiv2026

Interface-Controlled Spin-Orbit Torques in Rare-Earth Synthetic Ferrimagnets Probed by Sagnac Magneto-Optics and Harmonic Hall Measurements

Spin-orbit torque (SOT) provides an efficient route for manipulating magnetization in spintronic devices, and its accurate quantification is essential. Here, we investigate Co/Gd-based synthetic ferrimagnets using complementary magnetotransport and magneto-optical techniques. We use a Sagnac magneto-optical interferometry method to directly quantify current-induced magnetization tilting and extract the damping-like SOT effective field. The Sagnac measurements show good agreement with harmonic Hall analysis across different Co/Gd and Gd/Pt/Co heterostructures, providing a quantitative determination of the damping-like SOT effective field that does not rely on electrical transport signatures. By varying the Gd thickness and multilayer stacking order, we demonstrate that the damping-like torque is strongly influenced by spin transport and angular momentum conversion at rare-earth and heavy-metal interfaces. The observation of a finite torque in Gd/Pt/Co/Pt structures, where conventional Pt spin Hall contributions are expected to compensate, highlights the active role of the Gd layer in SOT generation. Furthermore, interface engineering enables perpendicular magnetic anisotropy in Gd/Pt/Co/Al heterostructures with a 2-nm-thick Co layer, allowing current-induced SOT switching at current densities of 8-10 MA/cm$^2$. These results establish rare-earth-based synthetic ferrimagnets as a versatile platform for engineering spin-orbit phenomena and optimizing low-power spintronic devices.

cond-mat.mtrl-sci↗

arXiv2026

Reflector-Free, Highly Confined Love-Like SAWs Enabled by a Phononic Metasurface for Real-Time Monitoring of Cell Dynamics

Surface acoustic wave (SAW) devices are widely used in sensing and biosensing but generally suffer from strong attenuation in liquid environments. Conventional approaches rely on reflectors to reduce these losses, yet these components remain difficult to optimize: limited device miniaturization, and increase fabrication complexity. Here, we introduce an innovative design strategy that integrates a phononic metasurface with tailored electromechanical properties of the substrate to generate a type of shear-horizontal (SH) surface resonance modes that exhibit strong lateral confinement and extremely low radiation into both the substrate bulk and the free surface, eliminating the need for reflectors. This approach enables highly tailorable surface acoustic resonances with distinctive enhanced dynamic strain-energy confinement leading to significantly higher quality factors than conventional SAW devices, particularly in water-loaded conditions. We show the fabrication and experimental validation of the proposed phononic metasurface-based SAW resonator and showcase its biosensing capabilities through real-time monitoring of cellular death.

physics.app-ph↗

arXiv2023

Spin-to-charge conversion by spin pumping in sputtered polycrystalline Bi$_x$Se$_{1-x}$

Topological materials are of high interest due to the promise to obtain low power and fast memory devices based on efficient spin-orbit torque switching or spin-orbit magnetic state read-out. In particular, sputtered polycrystalline Bi$_x$Se$_{1-x}$ is one of the materials with more potential for this purpose since it is relatively easy to fabricate and has been reported to have a very high spin Hall angle. We study the spin-to-charge conversion in Bi$_x$Se$_{1-x}$ using the spin pumping technique coming from the ferromagnetic resonance in a contiguous permalloy thin film. We put a special emphasis on the interfacial properties of the system. Our results show that the spin Hall angle of Bi$_x$Se$_{1-x}$ has an opposite sign to the one of Pt. The charge current arising from the spin-to-charge conversion is, in contrast, lower than Pt by more than one order of magnitude. We ascribe this to the interdiffusion of Bi$_x$Se$_{1-x}$ and permalloy and the changes in chemical composition produced by this effect, which is an intrinsic characteristic of the system and is not considered in many other studies.

cond-mat.mtrl-sci↗

arXiv2020

Flexible Over-Moded Resonators Based on P(VDF-TrFE) Thin Films With Very High Temperature Coefficient

This work presents for the first time a flexible over-moded resonator (OMR) based on P(VDF-TrFE) thin films. The devices were manufactured on commercially available elastic substrate with inkjet-printed electrodes. The sensing copolymer films used in the devices were polarized by the corona method after electrode deposition. The main performance parameters of the component were then determined. The manufactured OMRs on P(VDF-TrFE) exhibited a linear variation of frequency versus temperature and a very large value of temperature coefficient of frequency (TCF > 1600 ppm/degrees C). These properties suggest a great potential for using such components as low-cost and high-precision temperature sensors. The electromechanical coupling coefficient and the quality factor of the resonator were also characterized versus temperature.

physics.app-ph↗

arXiv2014

BiFeO3 nanocrystals for bio-imaging based on nonlinear optical harmonic generation

Second Harmonic Generation (SHG) from BiFeO3 nanocrystals is investigated for the first time to determine their potential as biomarkers for multiphoton imaging. Nanocrystals are produced by an auto-combustion method with TRIS as a fuel. Stable colloidal suspensions with mean particle diameters in the range 100-120 nm are then obtained after wet-milling and sonication steps. SHG properties are determined using two complementary experimental techniques, Hyper Rayleigh Scattering and nonlinear polarization microscopy. BiFeO3 shows a very high second harmonic efficiency with an averaged coefficient of 79+-12 pm/V. From the nonlinear polarization response of individual nanocrystals, relative values of the independent dij coefficients are also determined and compared with recent theoretical and experimental studies. Additionally, the particles show a moderate magnetic response, which is attributed to gamma-Fe2O3 impurities. A combination of high nonlinear optical efficiency and magnetic response within the same particle is of great interest for future bio-imaging and diagnostic applications.

physics.optics↗