Guebre Xaviher Tessema

Effect of elastic stress on the resistivity and Tc of (Bi, Pb)2Sr2Can−1CunOx

Abstract We have measured the effect of elastic uniaxial stress σ in the a direction on the superconducting transition temperature T c of (Bi, Pb) 2 Sr 2 Ca 1 Cu 2 O χ (2212) and (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O χ (2223). We find dT / dσ 11 =-10±2 K/GPa for 2212 and -6±2K/ GPa for the 2223 compound. Combining these results with those of others on d T c /d P we find that dT c / dσ 33 =+ 18 K/GPa. An estimate of the elastic constants of these compounds from the work of others together with these results implies that the change in T c with a fractional change in the c -axis spacing is probably positive, although the uncertainties in the elastic constants make this estimate subject to a large uncertainty. The resistance changes by less than 1 part in 12 000 for strains up to 0.5%, implying that dln ϱ / dσ 11 =-76 x 10 -3 GPa -1

Measure of the magnitude of Young's modulus in whisker-like samples of the Bi-based high-Tc materials Bi2Sr2CaCu2Ox and Bi2Sr2Ca2Cu3Ox

Abstract We have measured Youngs modulus in ribbon-like whisker samples of the high- T c materials: Bi 2 Sr 2 CaCu 2 O x and Bi 2 Sr 2 Ca 2 Cu 3 O x . This is the first direct measurement of Youngs modulus for whiskers of any of the high T c materials. We used a stress-strain probe that applies an axial force (uniaxial stress) to the whisker-like sample and simultaneously measures the corresponding sample elongation. The slope of the resulting stress-strain curve yields the magnitude of Youngs modulus ( Y ). We found these Bi based high- T c materials to be soft with Y ≈20 GPa for Bi 2 Sr 2 CaCu 2 O x and Y ≈25 GPa for Bi 2 Sr 2 Ca 2 Cu 3 O x .

Effect of magnetic substitutions Ni, Co, Fe for Cu on thermal conductivity of BiSCCO whiskers

Abstract We have measured the thermal conductivity κ of Bi2(SrCa)3(Cu1−xTx)2Oy (T=Ni,Co,Fe) whiskers containing up to 1.5% substitution for Cu. Increased substitution suppresses both Tc and the usual enhancement of κ seen below Tc in undoped samples. Additionally, substitution strongly decreases thermal transport by carriers which reveals the phonon thermal conductivity of Bi2(SrCa)3Cu2Oy. The phonon contribution was found to be glass-like and when subtracted from the measured κ allows a fit of the electronic thermal conductivity to a phenomenological model that includes partial condensation of carriers in Bi2(SrCa)3Cu2Oy.

The effect of Co substitution for Cu in Bi2Sr2Ca1Cu2O8-δ

Abstract We have grown single crystal whiskers of Bi 2 (SrCa) n +1 (Cu 1− x Co x ) n O 8− δ with 0 x R as a function of the temperature T . For x n =2 in the majority of the sample and n =3 in a small part. For both phases, the changes in T c and in the extrapolated residual resistance due to Co substitution are the same for Co as it is for Zn and Ni, indicating that magnetic scattering is not important. For x ≈0.06, oxygenation can drive the sample from superconducting to insulating, indicating that both the scattering of the carriers and the number of carriers affect the superconducting–insulating transition. This occurs in samples in which the sheet resistance in a CuO plane is approximately h /(2 e ) 2 . For x >0.18, the samples are insulating and n =1.

NBSE3 : EFFECT OF UNIAXIAL STRESS ON THE THRESHOLD FIELD AND FERMIOLOGY

We have measured the effect of elastic strain

Effect of elastic stress on the resistivity and Tc of (Bi, Pb)2Sr2Can−1CunOx for n = 2 or 3

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Thermoelectric Properties of M 2 Mo 6 Se 6 (M=TI, In)

on the threshold field

Magnetic properties of bulk Eu2/3Ca1/3MnO3

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Effect of elastic stress on the resistance of (Bi, Pb)2Sr2CaCu2CaCu2Ox single crystals☆

for the motion of the higher-temperature charge density wave (CDW) in

Effect of magnetic and nonmagnetic impurities (Ni, Zn) substitution for Cu in Bi{sub 2}(SrCa){sub 2+n}(Cu{sub 1{minus}x}M{sub x}){sub 1+n}O{sub y} whiskers

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