Transport properties of GdB6 and DyB6

The electrical resistance and absolute thermoelectric power (TEP) have been measured for GdB₆ and DyB₆ in the temperature range 2–30 K. The compounds GdB₆ and DyB₆ order antiferromagnetically atT _N 15.2 and 20.3 K, respectively. Above the Néel temperature the resistivity has a small contribution that is linear inT due to electron-phonon scattering, whereas in the same temperature range the spin-disorder TEP (S _spd) has been evaluated and found to be linear inT. A divergence in the temperature derivative of resistance and TEP has been found atT _N that is consistent with the present theories. There is evidence of a low-temperature phase appearing at 7 K in the resistivity and the TEP data of GdB₆. A minimum in the TEP is found in these compounds below 6 K, which is associated mainly with phonon drag and possibly a magnon contribution. A broad peak in the TEP of DyB₆ around 16 K is thought to be due to crystalline electric field effects.     

Macro- and Microdefects in Czochralski-Grown Li6GdB3O9 and Li6 – x Na x GdB3O9 Single Crystals

Macro- and microdefects in Czochralski-grown Li₆GdB₃O₉ crystals (unmodified and Na-modified) are investigated.     

Critical scattering around the antiferromagnetic transition in holmium

Detailed analyses of the electrical resistance of holmium near the antiferromagnetic transition T _N in magnetic fields up to 71 kOe are reported. The critical exponent in the expression for the reduced resistance % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9% Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaaieGacaWFYbacba% Gaa4hkaiaa-rhacaGFPaGaeyypa0Jaa8NCamaaBaaajeaqbaGaa4hm% aaWcbeaakiabgUcaRiaa-jeacaWF0bGaey4kaSIaa8xqamaaBaaale% aacqGHRaWkaeqaaOGaa8hDamaaCaaaleqabaGaa4xmaiabgkHiTGGa% aiab9f7aHbaakiabgUcaRiaa-feadaWgaaWcbaGaaeiiaiabgkHiTa% qabaGccaGFOaGaeyOeI0Iaa8hDaiaa+LcadaahaaWcbeqaaiaa+fda% cqGHsislcqqFXoqyaaaaaa!51B4!\[r(t) = r_0 + Bt + A_ + t^{1 - \alpha } + A_{{\rm{ }} - } ( - t)^{1 - \alpha } \] for % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9% Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaacqGHsislcaaIWa% GaaiOlaiaaigdacqGHKjYOcaWG0bGaeyizImQaaGymaiaac6cacaaI% 0aGaaeiiaGqaaiaa-HhacaWFGaGaa8xmaiaa-bdadaahaaWcbeqaai% abgkHiTiaaikdaaaaaaa!469D!\[ - 0.1 \le t \le 1.4{\rm{ }}x 10^{ - 2} \], where % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqaqpepeea0xe9qqVa0l% b9peea0lb9sq-JfrVkFHe9peea0dXdarVe0Fb9pgea0xa9pue9Fve9% Ffc8meGabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWG0bGaeyypa0% JaaiikaiaadsfacqGHsislcaWGubWaaSbaaKqaGfaaieaacaWFobaa% leqaaOGaaiykaiaac+cacaWGubWaaSbaaKqaGfaacaWFobaaleqaaa% aa!41DC!\[t = (T - T_N )/T_N \], is –0.27 for the c-axis crystal and is approximately field independent. The critical temperature decreases approximately linearly with increasing field. For T < T _N, the magnetoresistance exhibits a maximum and is negative at higher fields. These results have been interpreted in terms of field-induced changes in the spiral-spin structure and the estimated critical field is found to be in good agreement with published data.This research was supported in part by a grant from the Natural Sciences and Engineering Research Council of Canada.     

Critical light scattering in4He near the gas-liquid critical point

Scattered intensities of light were measured near the gas-liquid critical point of ⁴ He at scattering angles of 30, 60, and 90° as functions of the reduced temperature =|T–T _c |/T _c along the critical isochore (T>T _c ) and the coexistence curve (T>T _c ). The temperature range was 3×10 ^–5 <<1.5×10 ^–2 . Critical exponents and coefficients describing divergence of the generalized susceptibility and the correlation length are obtained as (T>T _c )=1.31±0.02, v(T>T _c )=0.66±0.02, ₀ (T>T _c )=4.2±0.6 Å, (T>T _c )=1.32±0.02, v(T>T _c )=0.68±0.02, _± (T>T _c )=2.6±0.7 Å, =0.06±0.06(T>T _c ), 0.05±0.05(T>T _c ), and ₀(T>T _c )/x_± (T>T _c )=3.6±0.4. It is pointed out that the quantal nature of ⁴ He has remarkable influence on the critical behavior of ⁴ He in the above-mentioned temperature region.     

Effect of grain-boundary scattering on the electrical resistivity of indium films

Electrical resistivity and temperature coefficient of resistivity of polycrystalline indium films have been studied in the temperature range 30 to 90 C. It has been observed that the grain-boundary scattering theory of Mayadas and Shatzkes reproduces the experimental observations more faithfully than the size-effect theory given by Fuchs.     

Annealing study of the electrical resistance and defect density in calcium films

Polycrystalline calcium films were deposited under ultrahigh vacuum onto a cooled silica substrate by thermal evaporation. During the growth process of the film a number of lattice defects are incorporated. In the present study, Vand's theory is applied and allows us to calculate the characteristic function F₀ expressing the law of distribution of the decay energies.     

Synthesis and characterization of single crystalline GdB44Si2 nanostructures

GdB₄₄Si₂ is an excellent thermoelectric material, and nanostructured GdB₄₄Si₂ makes it possible to potentially improve its properties further. GdB₄₄Si₂ nanowires and nanobelts have been fabricated by chemical vapor deposition and characterized by electron diffraction and high-resolution electron microscopy. These nanostructures are of the YB₅₀ structure and grew in the [010] direction. The nanowires have thickness of less than 100 nm and length of several tens of microns. The nanobelts have thickness of about a few tens of nanometers. Morphological and compositional analyses confirmed that the nanowire growth followed the vapor–liquid–solid mechanism and the nanobelts were formed by a subsequent vapor–solid process of condensation.     

Switching the electrical resistance of individual dislocations in single-crystalline SrTiO3

The great variability in the electrical properties of multinary oxide materials, ranging from insulating, through semiconducting to metallic behaviour, has given rise to the idea of modulating the electronic properties on a nanometre scale for high-density electronic memory devices. A particularly promising aspect seems to be the ability of perovskites to provide bistable switching of the conductance between non-metallic and metallic behaviour by the application of an appropriate electric field. Here we demonstrate that the switching behaviour is an intrinsic feature of naturally occurring dislocations in single crystals of a prototypical ternary oxide, SrTiO(3). The phenomenon is shown to originate from local modulations of the oxygen content and to be related to the self-doping capability of the early transition metal oxides. Our results show that extended defects, such as dislocations, can act as bistable nanowires and hold technological promise for terabit memory devices.     

Method of certifying electrical resistance measures in the audio frequency range

Measurement Techniques -     

Surface morphology and electrical resistance of the oxide film on InSe

Experimental evidence is presented that air oxidation of InSe crystals produces a native oxide layer which possesses not dielectric but conductive properties and is separated from the semiconductor substrate by a potential barrier. The surface resistance of oxide films grown on InSe across and along the C axis has been measured as a function of oxidation time and temperature. The results demonstrate that the surface resistance of the films varies significantly only during the first five minutes of oxidation. Subsequently, the surface resistance remains almost constant at 100–150 Ω/□. The surface morphology of the native oxide on InSe has been studied by atomic force microscopy. The oxide surface is shown to be nanotextured due to nanospikes normal to the substrate surface. The influence of oxidation temperature and time on the dynamics of the surface morphology of the oxide layer (the lateral dimensions, height, and density of nanospikes) is examined.     

Effect of grain boundary scattering on the electrical conductivity of antimony films

By starting from the theory of Mayadas and Shatzkes, a model for the effect of grain boundaries on the electrical conductivity of an intrinsic semimetal is proposed. The influence of the size of crystallites on the electrical conductivity of polycrystalline antimony films is studied theoretically and experimentally.

Excellent agreement is obtained over a large temperature range (10–500 K) for various sizes of crystallites (100–2000 Å).     

In-situ electrical resistance measurement of the selenization process in the CuInGa-Se system

In this work the selenization reactions and reaction paths in CuIn_xGa_1-xSe₂ thin films prepared by sputtering and post-selenization process are investigated. The in-situ electrical resistance measurement technique is applied to monitor all the selenization reactions. The crystal structure is determined by X-ray diffraction (XRD) measurement. From the analysis of resistance-temperature curves and the XRD patterns, the phase evolutions of various crystalline and selenization reaction paths have been obtained. From these measurements, the reaction mechanisms and kinetics in the CuInGa-Se system are further understood.     

Relationship of the electrical resistance of metals to their strength in heating

A review is given of literature sources on the use of data on the electrical conductivity of metals in studying their strength. It is shown that a correlation relationship between strength and electrical resistance is possible for relatively pure metals.Translated from Problemy Prochnosti, No. 8, pp. 89–92, August, 1990.