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Mechanical properties of lithium molybdate single crystals, Li2MoO4, are studied from room temperature to 650 °C. Density functional theory calculations gave the seven elastic constants of the rhombohedral crystal at 0 K. Brillouin light scattering experiments delivered comparable values at room temperature, and measurements up to 650 °C show a linear decrease in the constants with temperature. Nano-indentation results were typical of a brittle material with a low Young modulus and allowed deriving Young's moduli, for c (63 GPa) and m (48 GPa) faces, in agreement with those computed from measured elastic constants. Compressive rupture tests were performed. At 650 °C, the rupture stress was in the range 2–7.5 MPa. No clear evidence of a plastic regime was observed before cracking, even at temperatures close to the melting point. [ABSTRACT FROM AUTHOR]

This paper presents the prospects for periodic magnetic nanostructures in the form of magnonic crystals on polymer substrates. Indeed, arrays of magnetic nanostructures on flexible substrates are promising for microwave applications in the GHz frequency range. In particular, the mastery of the potentially coupled physical properties (magnetic and mechanical) allows one to consider devices for microelectronics in general, combining the microwave properties of spin waves with the lightness and conformability of polymer substrates. However, there are still scientific hurdles to be overcome, particularly with regard to the reliability of these systems, which is the focus of this review. Subsequently, we propose a general state of the art, a summary of the precursor works, and a general strategy for the optimization of these systems and their future possibilities. [ABSTRACT FROM AUTHOR]

Metallic thin films deposited onto polymeric substrates find important technological applications as stretchable microelectronic devices. Academic research on these systems has mainly focused on uniaxial tensile tests, though biaxial stress states are generally applied during service. We study in this article the strain ratio effect on nanocrystalline 50 nm-thick gold thin films supported on a polyimide: equibiaxial applied strain vs uniaxial applied strain. The mechanical behaviors are compared with digital image correlation, x-ray diffraction, and relaxation tests, giving the true and lattice strains, insights into strain heterogeneities, and leading plasticity mechanisms. Moreover, two load–unload cycles were performed to deconvolute the different parts contributing to the signals. It is shown that though the samples were transversely isotropic (i.e., isotropic in the plane of the applied strains), the work-hardening properties are very different, the micro-plastic regime being greatly reduced in the equibiaxial test. This is illustrated with the elastic limits and with the fact that an equibiaxial test presents at equivalent von Mises strain higher stress relaxation and a decrease in strain heterogeneities. [ABSTRACT FROM AUTHOR]

In our work, we study the physical origins of the hydrogen gas induced reduction of the strength of perpendicular magnetic anisotropy (PMA) at the interface of cobalt and palladium layers. To this end, we grow these films on flexible substrates and carry out ferromagnetic resonance (FMR) measurements in the presence of two different stimuli—hydrogen gas and elastic strain. Exposing the samples to H2 results in a downshift of the FMR field. On the contrary, FMR measurements carried out in the presence of an externally applied predominantly tensile elastic stress show an up-shift in the resonance field consistent with negative values of the saturation magnetostriction coefficient for our samples. Qualitative analysis of these results demonstrates that the magneto-elastic contribution to the hydrogen-induced change in PMA is very small and is of the opposite sign to the electronic contribution related to the influence of hydrogen ions on the hybridisation of cobalt and palladium orbitals at the interface. [ABSTRACT FROM AUTHOR]

Performing a complete in-situ strain measurement of polycrystalline thin films using X-ray diffraction is time consuming with most standard diffraction beamlines at synchrotron facilities and not realistic with laboratory diffractometers. Two dimensional detection is shown to enable relatively fast and reliable X-ray strain measurements during continuous in-situ tensile testing of metallic films deposited on polyimide substrates. We show in this paper the advantages to perform this kind of measurements as compared to those with punctual detection.

The mechanical behaviour of multilayered W/Cu thin films on polyimide substrate has been investigated at different scales and using complementary X-ray techniques and compared to finite element analysis. Mechanical testing has been carried out using a new biaxial tensile machine which allows for testing in controlled biaxial loading condition. This device has been developed for synchrotron measurements at DiffAbs beamline of the French synchrotron radiation facility (SOLEIL, Saint Aubin).

(Received 5 July 2014; accepted 22 August 2014; published online 4 September 2014) Comparative studies of the mechanical behavior between copper, tungsten, and W/Cu nanocomposite based on copper dispersoïd thin films were performed under in-situ controlled tensile equi-biaxial loadings using both synchrotron X-ray diffraction and digital image correlation techniques. The films first deform elastically with the lattice strain equal to the true strain given by digital image correlation measurements. The Cu single thin film intrinsic elastic limit of 0.27% is determined below the apparent elastic limit of W and W/Cu nanocomposite thin films, 0.30% and 0.49%, respectively. This difference is found to be driven by the existence of as-deposited residual stresses. Above the elastic limit on the lattice strain-true strain curves, we discriminate two different behaviors presumably footprints of plasticity and fracture. The Cu thin film shows a large transition domain (0.60% true strain range) to a plateau with a smooth evolution of the curve which is associated to peak broadening. In contrast, W and W/Cu nanocomposite thin films show a less smooth and reduced transition domain (0.30% true strain range) to a plateau with no peak broadening. These observations indicate that copper thin film shows some ductility while tungsten/copper nanocomposites thin films are brittle. Fracture resistance of W/Cu nanocomposite thin film is improved thanks to the high compressive residual stress and the elimination of the metastable β-W phase. [ABSTRACT FROM AUTHOR]

Magnetic properties of Co2MnGe thin films of different thicknesses (13, 34, 55, 83, 100, and 200 nm), grown by rf sputtering at 400 °C on single crystal sapphire substrates, were studied using vibrating sample magnetometry and conventional or microstrip line ferromagnetic resonance. 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 miscut angle of the Al2O3 substrate. The twofold in-plane anisotropy field Hu is almost temperature independent, in contrast with the fourfold field H4 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 α value of 0.0065 for the 55-nm-thick film. [ABSTRACT FROM AUTHOR]