Voltage-induced strain control of the magnetic anisotropy in a Ni thin film on flexible substrate

Voltage-induced magnetic anisotropy has been quantitatively studied in polycrystalline Ni thin film deposited on flexible substrate using microstrip ferromagnetic resonance. This anisotropy is induced by a piezoelectric actuator on which the film/substrate system was glued. In our work, the control of the anisotropy through the applied elastic strains is facilitated by the compliant elastic behavior of the substrate. The in-plane strains in the film induced by the piezoelectric actuation have been measured by the digital image correlation technique. Non-linear variation of the resonance field as function of the applied voltage is found and well reproduced by taking into account the non linear and hysteretic variations of the induced in-plane strains as function of the applied voltage. Moreover, we show that initial uniaxial anisotropy attributed to compliant substrate curvature is fully compensated by the voltage induced anisotropy.Comment: 7 pages, 6 figures, published in the Journal of Applied Physic

Micro-strip ferromagnetic resonance study of strain-induced anisotropy in amorphous FeCuNbSiB film on flexible substrate

The magnetic anisotropy of a FeCuNbSiB (Finemet) film deposited on Kapton has been studied by micro-strip ferromagnetic resonance technique. We have shown that the flexibility of the substrate allows a good transmission of elastic strains generated by a piezoelectric actuator. Following the resonance field angular dependence, we also demonstrate the possibility of controlling the magnetic anisotropy of the film by applying relatively small voltages to the actuator. Moreover, a suitable model taking into account the effective elastic strains measured by digital image correlation and the effective elastic coefficients measured by Brillouin light scattering, allowed to deduce the magnetostrictive coefficient. This latter was found to be positive $(\lambda=16\times10^{-6}$) and consistent with the usually reported values for bulk amorphous FeCuNbSiB.Comment: 9 pages, 8 figure

Structural, static and dynamic magnetic properties of CoMnGe thin films on a sapphire a-plane substrate

Magnetic properties of CoMnGe thin films of different thicknesses (13, 34, 55, 83, 100 and 200 nm), grown by RF sputtering at 400{\deg}C on single crystal sapphire substrates, were studied using vibrating sample magnetometry (VSM) and conventional or micro-strip line (MS) ferromagnetic resonance (FMR). Their behavior is described assuming a magnetic energy density showing twofold and fourfold in-plane anisotropies with some misalignment between their principal directions. For all the samples, the easy axis of the fourfold anisotropy is parallel to the c-axis of the substrate while the direction of the twofold anisotropy easy axis varies from sample to sample and seems to be strongly influenced by the growth conditions. Its direction is most probably monitored by the slight unavoidable angle of miscut the Al2O3 substrate. The twofold in-plane anisotropy field is almost temperature independent, in contrast with the fourfold field which is a decreasing function of the temperature. Finally, we study the frequency dependence of the observed line-width of the resonant mode and we conclude to a typical Gilbert damping constant of 0.0065 for the 55-nm-thick film.Comment: 7 pages, 7 figures, To be published (Journal of Applied Physics

Combined synchrotron X-rays and image correlation analyses of biaxially deformed W/Cu nanocomposite thin films on Kapton

International audienceAbstract In-situ biaxial tensile tests within the elastic domain were conducted with W/Cu nanocomposite thin films deposited on a polyimide cruciform substrate thanks to a biaxial testing machine developed on the DiffAbs beamline at SOLEIL synchrotron. The mechanical behavior of the nanocomposite was characterized at the micro-scale and the macro-scale using simultaneously synchrotron X-ray diffraction and digital image correlation techniques. Strain analyses for equi-biaxial and non equi-biaxial loading paths have been performed. The results show that the two strain measurements match to within 1 × 10-4 in the elastic domain for strain levels less than 0.3% and for both loading paths

Magnetic domain-wall motion study under an electric field in a Finemet thin film on flexible substrate

Influence of applied in-plane elastic strains on the static magnetic configuration of a 530 nm magnetostrictive FeCuNbSiB thin film. The in-plane strains are induced via the application of a voltage to a piezoelectric actuator on which the film/substrate system was glued. A quantitative characterization of the voltage dependence of the induced-strain at the surface of the film was performed using a digital image correlation technique. MFM images at remanence (H=0 Oe and U=0 V) clearly reveal the presence of weak stripe domains. The effect of the voltage-induced strain shows the existence of a threshold value above, which the break of the stripe configuration set in. For a maximum strain of exx~0.5*10-3 we succeed in destabilizing the stripes configuration helping the setting up of a complete homogeneous magnetic pattern.Comment: 5 pages, 4 figures, to appear in J. Mag. Mag. Ma

Suivi par diffraction des hétérogénéités de déformation dans un acier duplex

To validate mean- and full-field micromechanical models, we have performed elastic strain measurements using several diffraction techniques (neutrons,transmission and reflexion under synchrotron radiation, and laboratory X-ray) during which the specimen was tensile deformed in-situ. Application has been performed on a duplex steel (ferrite and austenite) as an example of two-phase high-strength polycrystals. The uncertainty and relevance of the different measurements will be discussed and compared with simulations based on an elasto-viscoplastic self-consistent model

Elastic-strain distribution in metallic film-polymer substrate composites

Synchrotron x-ray radiation was used for in situ strain measurements during uniaxial tests on polymer substrates coated by a metallic gold film 400 nm thick deposited without interlayer or surface treatment. X-ray diffraction allowed capturing both components elastic strains and determining how these were partitioned between the metallic film and the polymeric substrate. For strains below 0.8%, deformation is continuous through the metal-polymer interface while above, the onset of plasticity in the metallic film induces a shift between film and substrate elastic strains

X-ray strain analysis of {111} fiber-textured thin films independent of grain-interaction models

The anisotropic elastic response of supported thin films with a {111} fiber texture has been studied using an in-situ micro-tensile tester and X-ray diffractometry. It is shown which specific X-ray diffraction measurement geometries can be used to analyze the elastic strains in thin films without requiring any assumptions regarding elastic interactions between grains. It is evidenced (theoretically and experimentally) that the combination of two specific geometries leads to a simple linear relationship between the measured strains and the geometrical variable sin 2 , avoiding the transition scale models. The linear fit of the experimental data allows a direct determination of the relationship between the three single-crystal elastic compliances or a direct determination of the S 44 single-crystal elastic compliance and the combination of S 11 + 2S 12 if the macroscopic stress is known. This methodology has been applied to a model system, i.e. gold film for which no size effect is expected, deposited on polyimide substrate, and it was found that S 44 = 23.2 TPa -1 and S 11 + 2S 12 = 1.9 TPa -1 , in good accordance with values for large crystals of gold. © 2011 International Union of Crystallography Printed in Singapore - all rights reserved

Elastic anisotropy of polycrystalline Au films: Modeling and respective contributions of X-ray diffraction, nanoindentation and Brillouin light scattering

Elastic properties of non-textured and {1 1 1}-fiber-textured gold thin films were investigated experimentally by several complementary techniques, namely in situ tensile testing under X-ray diffraction (XRD), nanoindentation and Brillouin light scattering (BLS). Specimens were probed along different directions to reveal the strong effects of elastic anisotropy at the (local) grain and (global) film scales. XRD allows the investigation of both local and global anisotropies, while BLS and nanoindentation are limited to global analyses. A micromechanical model, based on the self-consistent scheme, and accounting for the actual microstructure of the films, is applied to interpret experimental data. Although different types of elastic constants can be determined with the used experimental techniques (static/dynamic, local/global), a good agreement is obtained, showing that comparison of these techniques is feasible when carried out carefully. In particular, the use of a micromechanical model to estimate the effects of the local elastic anisotropy at the film scale is unavoidable. The presented results show that XRD, BLS and nanoindentation should capture anisotropic texture effects on elastic constants measurements for materials with a Zener anisotropy index larger than 2. Conversely, the actual texture of a given specimen should be taken into account for a proper analysis of elastic constants measurements using those three experimental techniques