Sudook Kim

Contactless Mode-Selective Resonance Ultrasound Spectroscopy: Electromagnetic Acoustic Resonance

A noncontacting resonant-ultrasound-spectroscopy (RUS) method for measuring elastic constants and internal friction of conducting materials is described, and applied to monocrystalline copper. This method is called electromagnetic acoustic resonance (EMAR). Contactless acoustic coupling is achieved by energy transduction between the electromagnetic field and the ultrasonic vibrations. A solenoidal coil and static magnetic field induce Lorentz forces on specimen surfaces without using a coupling agent. By changing the field direction, a particular set of vibration modes can be selectively excited and detected, an advantage in identifying the vibration modes of the observed resonance peaks. Contactless coupling allows the measure of intrinsic internal friction free from energy loss associated with contact coupling. The elastic constants and internal friction measured by EMAR are compared with those by the usual RUS method for a rectangular-parallelepiped copper monocrystal. Both methods yielded the same ela...

Elastic constants of natural quartz

The elastic constants of a natural-quartz sphere using resonance-ultrasound spectroscopy (RUS) are measured. The measurements of the near-traction-free vibrational frequencies of the sphere are matched with the predicted frequencies from the dynamic theory of elasticity, with optimized estimates for the elastic constants driving the differences between these sets of frequencies to a minimal value. The present computational model, although based on earlier approaches, is the first application of RUS to trigonal-symmetry spheres. Quartz shows six independent elastic constants, and our estimates of these constants are close to those computed by other means. Except for C14, after a 1% mass-density correction, natural quartz and cultured quartz show the same elastic constants. Natural quartz shows higher internal frictions.

Elastic constants, debye temperatures, and electron-phonon parameters of superconducting cuprates and related oxides

Abstract Using both measurements and modeling, we studied the cohesive and related properties of several oxides. Superconducting oxides include La1.85Sr0.15CuO4, Y1Ba2Cu3O7, and (Bi-Pb)2Sr2Ca2Cu3O10. Related nonsuperconducting oxides include SrTiO3, BaTiO3, and La2CuO4. For these materials, we give the complete quasiisotropic elastic constants corrected to the void-free state. From elastic constants and atomic volume, we calculated Debye characteristic temperatures, Θ D . Using Kresins model, valid for all values of the electron-phonon parameter, λ, we estimated I from Tc and Θ D . For the superconducting cuprates, λ ranges from 1.3 (La-O) to 10.0 (Tl-O). Except perhaps for Tl-O, these parameters fall within a range predicted by theory. For all the above materials, we show the 295–5-K variation of Θ D . We support our elastic-constant measurements with Born-model calculations of the bulk modulus.

Elastic constants of body-centered-cubic titanium monocrystals

We report estimates of body-centered-cubic titanium’s monocrystal elastic constants C11, C12, and C44. Two constants resulted from measuring a pure-titanium polycrystal at high temperatures using resonant-ultrasound spectroscopy. The third constant resulted from assuming a Zener elastic anisotropy and using inversely Kroner’s monocrystal–polycrystal elastic-constant relationship. Our values are C11=97.7, C12=82.7, and C44=37.5 GPa at 1000 °C.

Characterization of magnetic properties at edges by edge-mode dynamics

We have used “trapped spin wave” or edge modes of magnetic precession to probe the magnetic environment near magnetic film edges magnetized perpendicular to the edge. Micromagnetic models of dynamics in stripes reveal that the edge mode frequency-field relationship depends on whether the edge surface is vertical or tapered, while the “bulk” modes are nearly unaffected. The models show the edge-mode frequency going to zero at the edge saturation field. This critical field becomes much less distinct for applied fields misaligned from the edge normal by as little as 1°. Ferromagnetic-resonance and Brillouin light-scattering measurements of the edge modes in an array of 480-nm-wide×12-nm-thick Ni80Fe20 stripes have a lower edge saturation field than the vertical edge models, but agree well with the model of 45°-tapered edges.

Low-temperature elastic coefficients of polycrystalline indium

Abstract Using an ultrasonic pulse-echo method, we measured the elastic coefficients of polycrystalline indium from 300 to 5 K. All elastic coefficients showed regular temperature behavior, as predicted by an Einstein-oscillator model. The shear and Young moduli showed the largest change, increasing ≈55% during cooling. The Poisson ratio was unusually high at 0.45, just below the theoretical upper bound of 0.5. Using a Marx composite oscillator, we measured the internal friction at room temperature. We calculated the acoustic Debye temperature, 108.4 K, that agreed well with a monocrystal acoustic value, 111.3 K and the specific-heat value, 108.8 K. Also, we calculated the Gruneisen parameters, γL=2.04, γH=2.68, that agreed well with the specific-heat value, γ=2.48 and the shock-wave value, γ=2.24.

Low temperature elastic constants of deformed polycrystalline copper

Abstract By ultrasonic methods, we studied coppers elastic constants between 295 and 4 K. The specimens consisted of polycrystals deformed by rolling. At ambient temperature, compared with annealed texture-free copper, the deformed specimens usually showed lower elastic stiffness: up to 11% in Youngs modulus and 19% in shear modulus. The Poisson ratio increased up to 14%. These softenings reflect three internal-structure changes: texture, non-pinned dislocation density and anisotropic dislocation array. Cooling to 4 K showed regular behavior, nearly the same as for annealed texture-free copper. After plastic deformation, at ambient temperatures, the elastic constants showed time-dependent recovery.

Mode-selective resonance ultrasound spectroscopy of a layered parallelepiped

The resonance frequencies of mechanical free vibration of a three-layer material calculated by a discrete-layer model and measured by acoustic-resonance methods were compared. The material was composed of an aluminum parallelepiped sandwiched by two stainless-steel parallelepipeds. The discrete-layer model developed here used linear Lagrange basis functions through the layered dimension and continuous global power-series basis functions in the plane perpendicular to the layer thickness. Using such a basis function for the layer-thickness direction allows discontinuity in the elastic properties across the interface between dissimilar layers. The resonance frequencies were measured using two methods: mode-selective electromagnetic acoustic resonance (EMAR) and resonance ultrasound spectroscopy (RUS). The measurements agreed with the calculations typically within 1%. The EMAR method allows the selective detection of vibrational modes possessing particular displacement patterns. This selectivity was supported...

Anelastic loss in langatate

Anelastic loss in langatate (La/sub 3/Ga/sub 5.5/Ta/sub 0.5/O/sub 14/) was measured as a function of temperature from 80 to 1080 K at ultrasonic frequencies from 0.5 to 1.8 MHz. The specimens were monocrystalline cylinders with the trigonal axis parallel to the cylinder axis. Q/sup -1/ and the resonant frequencies were measured with inductive electromagnetic-acoustic and contacting transduction techniques. On cooling from room temperature to 80 K, Q/sup -1/ decreased by approximately an order of magnitude, with the most rapid drop occurring in the 220-260 K range. Part of this temperature dependence may result from the phonon-phonon interaction. However, the frequency dependence of Q/sup -1/ at room temperature is inconsistent with theories for the phonon-phonon interaction, and Qf at room temperature is much lower than values at higher frequencies reported by other researchers. These results suggest that Q/sup -1/ measured at and below room temperature is dominated by an anelastic defect contribution, rather than the intrinsic phonon-phonon damping. Dislocation damping is considered the most likely candidate for this contribution. At elevated temperatures, a relaxation peak appears with a maximum in the 750-810 K range for frequencies between 0.5 and 1.8 MHz. The activation energy of the relaxation is 1.1 eV, which is typical of point-defect relaxations. A second peak appears near 860 K during the first heating and disappears after heating to 1080 K. The observed peaks rise above a background that increases rapidly at the highest temperatures. By analogy with a similar effect observed in quartz, this background is assumed to arise from the anelastic relaxation of diffusing interstitial impurities.

Acoustic study of texture in polycrystalline brass

Resonant ultrasound spectroscopy was used to measure the orthorhombic elastic constants of rolled, polycrystalline plates of Cu, Cu–5% Zn, and Cu–15% Zn. The experimental results were fit to theoretical expressions to determine the orientation-distribution coefficients W400, W420, and W440. These coefficients are related to texture (the nonrandom orientation of crystallites). The experimental results were in good agreement with theory for the Cu and the Cu–15% Zn materials. The agreement was not as good for the more anisotropic Cu–5% Zn material, especially for the in-plane compressional constants C11 and C22. The ultrasonically derived W’s were compared to those obtained from neutron measurements for the Cu–Zn alloys. Pole plots based on the two types of measurements, using W400, W420, and W440, were in excellent agreement for the 15% Zn material, and in qualitative agreement for the 5% Zn material. The results support the idea that acoustic methods can be used to measure the low-order W’s in polycrystal...