Effect Of Uniaxial Mechanical Stress Research Articles

The effect of uniaxial mechanical stress on electronic and dynamic properties of silicon

The effect of uniaxial mechanical stress on electronic and dynamic properties of silicon

The Effect of Mechanical Stresses on the Coercive Force of the System of Two-Phase Interacting Nanoparticles

Within the framework of the two-phase grain model (by the example of γ-Fe203 cobalt coated particles) a theoretical analysis of the effect of uniaxial mechanical stresses on the magnetization of the system of hetero-phase interacting nanoparticle was held. It is shown that stretching leads to reduction when compression increases the coercive force Hc and doesnt change the residual saturation magnetization Irs of the system of interacting particles. "Smoothing" the hysteresis loop and "lowering" the magnetization curve, the magnetostatic interaction between particles decreases both Hc, and Irs, giving the fact that hysteresis characteristics of an ensemble of interacting nanoparticles change much more in stretching than in compression.

Effect of Mechanical Stress on Magnetic States and Hysteresis Characteristics of a Two‐Phase Nanoparticles System

In terms of the two‐phase nanoparticles model, the effect of mechanical stress on the magnetic state of both uniaxial and multiaxial heterophase magnetic is investigated. The spectrum of critical fields of reversal of phases′ magnetic moments was calculated and phase diagrams were drawn to assess the effect of mechanical stress on the degree of metastability of two‐phase nanoparticles′ magnetic states. By the example of epitaxial cobalt‐coated γ‐Fe2O3 particles, a theoretical analysis of the effect of uniaxial mechanical stress on the magnetization of a system of noninteracting heterophase nanoparticles is investigated. It was shown that tension reduced and compression increased coercive force Hc, while the residual saturation magnetization Irs was not changed under the influence of mechanical stress.

Effect of mechanical stresses on the initial susceptibility and hysteresis characteristics of an ensemble of nanoparticles

Effect of uniaxial mechanical stresses on the initial susceptibility, saturation remanence, and coercive force of materials in which single-domain nanoparticles are carriers of magnetic properties has been studied theoretically. It has been shown that at small elastic stresses the above characteristics vary linearly; with increasing stresses, the growth of tensile stresses leads to a nonmonotonic variation of these characteristics, and the growth of compressive stresses, to a continuous decrease in the susceptibility and remanence and to an increase in the coercive force. With increasing plastic deformations, the position of the maximum in the stress dependence of the saturation remanence (or initial susceptibility) and the position of the minimum in the coercive force dependence are shifted to the region of greater values.

The baric changes of the refractive properties of K_{2}SO_{4} crystals

The dependencies of the birefringenceni of K2SO4 crystals in wide spectral (250-800 nm) ranges, as well as the effect of uniaxial mechanical stress on them have been studied. The values of ni for K2SO4 are found to be rather sensitive to the uniaxial stress. The spectral characteristics of the refractive indices ni of free and mechanically clamped K2SO4 crystals have been studied. The refractive indices turned out to increase under the effect of uniaxial stress. The variations in the refraction, electron polarizability and the position of the center of the effective ultraviolet absorption band have been calculated. It is shown that the positions of the isotropic points in these crystals can be controlled by thermal and spectral methods.

The Refractive Properties of Uniaxially Stressed Doped TGS Crystals

The effect of uniaxial mechanical stresses applied along the principal crystal-physical axes on the principal values of birefringence Δ n i is studied on TGS crystals with L-threonine, L-valine and D-serine admixtures. It is revealed that Δ n i are quite sensitive to the stresses and have different values and opposite signs. The baric coefficients ∂Tc/∂ σm for the phase transition (PT) temperature appear to be smaller than those for the pure TGS crystals. Temperature and spectral dependences of the combined piezooptic constants are calculated.

The Baric Changes of the Electron Polarisability of LiRbSO4, LiKSO4 and (NH4)2BeF4 Crystals

The effect of uniaxial mechanical stresses on the spectral and temperature dependences of principal refractive indices n i and birefringence Δ n i of LiRbSO4, LiKSO4 and (NH4)2BeF4 crystals have been studied in the wide spectral (250–800 nm) and temperature (100–800 K) ranges. Displacements of the PT points under the uniaxial stress action as well as both an extensition or narrowing of the temperature intervals of the incommensurate phase have been revealed. The baric increacement of the n i was observed.

THE REFRACTOMETRY OF THE UNIAXIALLY STRESSED FERROELECTRICS

The effect of uniaxial mechanical stresses upon the spectral and temperature dependences of birefringences in some ferroelectric crystals with the incommensurate phase are studied. Considerable baric displacements of para-incommensurate-commensurate phases transition points were observed.The calculated temperature and spectral dependences of combined π im and absolute πim piezooptic constants show a considerable dispersion and anomalies at phase transitions.The increase of the principal refractive indices under stress effect was observed.

Effect of uniaxial mechanical stress on Shubnikov-de Haas oscillations in hole channels of silicon field-effect transistors

A study is made of the effect of uniaxial mechanical stress on Shubnikov-de Haas oscillations in two-dimensional hole channels of silicon field-effect transistors. It is shown that the main effect of the stress is a shift of the node of the beats of the oscillations. This shift corresponds in the case of compression (tension) to an increase (decrease) of the spin splitting in a zero magnetic field. In the case of two filled size-quantization subbands a mechanical stress of either sign causes a small fraction of the carriers to be transferred from the lower into the upper subband.

Stress dependence of coercivity in Ni films: Thin film to bulk transition

The effect of uniaxial mechanical stress on the magnetic properties of electroplated Ni films was measured with a magneto-optical Kerr loop tracer. We show that the effect of stress on the coercive force is completely different for thin (20 nm) and thick (10 μm) films. The latter behaves like bulk Ni, whereas results on lower thicknesses show a continuous transition from thin film to bulklike behavior. The results are discussed by assuming different micromagnetic reversal processes for the two extremes: rotational for thin film and domain wall movement for bulk.

Piezo-Hall coefficients of n-type silicon

The effect of uniaxial mechanical stress on the Hall coefficient of n-type silicon has been measured for various crystallographic orientations, and piezo-Hall coefficients P12 and P11-P44 have been derived for electron concentrations n between 1014 and 1016 cm−3 and temperatures ranging from −80 to +100 °C. In this range the piezo-Hall effect is found to be as important as the piezoresistance effect which is understood in terms of the many-valley band structure of silicon with anisotropic energy minima. For Hall plates in the (100) and the (110) plane of silicon the resulting longitudinal and transverse piezo-Hall coefficients at room temperature are plotted as a function of their orientation in the plane. It turns out that the piezo-Hall as well as the piezoresistance effects are minimized for a Hall plate in the (110) plane with the current flow roughly parallel to 〈11̄1〉.