Pressure dependence of upper critical fields in FeSe single crystals

Anisotropies of the lower and upper critical fields in MgB2 single crystals.

The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately ...

Upper critical field of high-quality single crystals of KFe2As2

Measurements of temperature-dependent in-plane resistivity ρ(T) were used to determine the upper critical field and its anisotropy in high-quality single crystals of the stoichiometric iron arsenide superconductor KFe2As2. The crystals were characterized by the residual resistivity ratio ρ(300 K)/ρ(0) up to 3000 and the resistive transition midpoint temperature Tc=3.8 K, significantly higher th...

Upper and lower critical magnetic fields of superconducting NdFeAsO1–xFx single crystals studied by Hall-probe magnetization and specific heat

Pressure Dependence of Damping Constant of Dislocation Motion in Crystals

Ultrasonic attenuation in Harshaw LiF and NaCl crystals in deformed and y-irradiated states has been measured at 5 a 100 MHz under hydrostatic pressure up to 3500 kg/cmz. By analyzing the data on the basis of the vibrating string model of dislocation, the pressure derivative of damping constant for dislocation motion was determined. The results were compared with theories of dislocation damping...

Hydrostatic and uniaxial pressure dependence of superconducting transition temperature of KFe2As2 single crystals

We present heat capacity, c-axis thermal expansion and pressure-dependent, low-field, temperature-dependent magnetization for pressures up to ∼12 kbar, data for KFe2As2 single crystals. Tc decreases under pressure with dTc/dP≈−0.10 K/kbar. The inferred uniaxial, c-axis, pressure derivative is positive, dTc/dpc≈0.11 K/kbar. The data are analyzed in comparison with those for overdoped Fe-based su...