MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS X—ESR OF Gd IN Y-Ba-Cu-O BETWEEN ABOUT Tcand 600°C

1992 ◽  
Vol 06 (24) ◽  
pp. 1525-1530 ◽  
Author(s):  
K. SUGAWARA ◽  
S. TANAKA
Keyword(s):  
Temperature Gradient ◽  
Temperature Dependence ◽  
Inhomogeneous Magnetic Field ◽  
Linear Temperature Dependence ◽  
High Temperature Side ◽  
Linear Temperature ◽  
High Tc ◽  
Absorption Studies ◽  
Zero Resistance ◽  
Temperature Side

Temperature dependence of ESR linewidth, ΔHPP, of Gd3+ in Y1−xGdxBa2Cu3Oy (x=0.2, 0.5 and 1) has been studied between about Tc (zero-resistance temperature) and about 600°C. For all the samples, ΔHPP progressively broadens as temperature approaches Tc from high temperature side, presumably due to inhomogeneous magnetic field distributions arising from superconductivity. On the contrary, ΔHpp is nearly linear in temperature between about 100 K and 600 K with temperature gradient, ∂(ΔHPP)/∂T~0.6 G/deg. The linear temperature dependence is assumed to be due to the Korringa relation. From the temperature gradient obtained above, JN(EF) was estimated as 0.0025, where J is the coupling coefficient between Gd spin S and conduction carrier’s spin S, and N(EF) is the density of states on the Fermi surface. In addition, by substituting an appropriate value for J, N(EF) was crudely estimated for the Y-Gd-Ba-Cu-O system.

DYNAMICS OF TWIN BOUNDARIES AND HIGH Tc SUPERCONDUCTORS

1987 ◽  
Vol 01 (03n04) ◽  
pp. 931-940
Author(s):  
B. Horovitz ◽  
G.R. Barsch ◽  
J.A. Krumhansl
Keyword(s):  
Specific Heat ◽  
Temperature Dependence ◽  
Electronic Properties ◽  
Twin Boundary ◽  
Linear Temperature Dependence ◽  
High Tc Superconductors ◽  
Linear Temperature ◽  
High Tc ◽  
Vertex Corrections ◽  
Anisotropic Dispersion

The formation of coherent arrays of twins in a tetragonal to orthorhombic transition and its effects on electronic properties are studied. The twin boundary oscillations (“dyadons”) have an anisotropic dispersion with frequencies typically ≲1010 sec −1 for wavevectors perpendicular to the boundaries. This results in a ~T2 contribution to the specific heat for T≳ 1° K and a linear temperature dependence of the resistivity. The unusual anisotropy yields vertex corrections which diverge at high temperatures and can enhance T c.

ANALYSIS OF MAGNETIC CRITICAL FIELDS IN IRON-BASED SmFeAsO0.85 HIGH-Tc SUPERCONDUCTOR

2011 ◽  
Vol 25 (24) ◽  
pp. 1939-1948 ◽  
Author(s):  
DAWOOD AHMAD ◽  
TAE KWON SONG ◽  
IN SUK PARK ◽  
G. C. KIM ◽  
ZHI-AN REN ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Low Temperatures ◽  
Irreversibility Line ◽  
Linear Temperature Dependence ◽  
Critical Fields ◽  
Linear Temperature ◽  
High Tc ◽  
High Tc Superconductor ◽  
Pressure Synthesis ◽  
Iron Based

The magnetic properties of the newly discovered iron-oxypnictide SmFeAsO 0.85 high-Tc superconductor with a Tc of around 55 K were investigated. Bulk SmFeAsO 0.85 was prepared by a method for high-pressure synthesis. The lower critical field H c1 was estimated from the magnetization at low fields; H c1 (0) was measured to be 212 Oe. A linear temperature dependence instead of saturation at low temperatures in H c1 (T) revealed unconventional superconductivity with a nodal gap structure in our SmFeAsO 0.85 superconductor. The results showed that the well-known secondary peak in the temperature dependence of the critical current density Jc is absent in the SmFeAsO 0.85 high-Tc superconductor. The irreversibility line B irr was fitted well by the power law dependence (1 - T/Tc)n with n ~ 1.5. This is indicative of the flux creep phenomena in the SmFeAsO 0.85 high-Tc superconductor. In addition, within the range of measurement temperatures in this study, no crossover was observed in the temperature dependence of the irreversibility line B irr which may be due to low anisotropy in our SmFeAsO 0.85 superconductor.

scholarly journals Linear temperature dependence of resistivity and change in the Fermi surface at the pseudogap critical point of a high-Tc superconductor

2008 ◽  
Vol 5 (1) ◽  
pp. 31-34 ◽  
Author(s):  
R. Daou ◽  
Nicolas Doiron-Leyraud ◽  
David LeBoeuf ◽  
S. Y. Li ◽  
Francis Laliberté ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Temperature Dependence ◽  
Critical Point ◽  
Linear Temperature Dependence ◽  
Linear Temperature ◽  
High Tc ◽  
High Tc Superconductor

Parametric Models of Ultrasonic Piezoelectric Transducers over a Wide Temperature Range

2015 ◽  
Vol 2015 (HiTEN) ◽  
pp. 000266-000272 ◽  
Author(s):  
Steven A. Morris ◽  
Jeremy Townsend
Keyword(s):  
Dielectric Constant ◽  
Temperature Dependence ◽  
Coupling Coefficient ◽  
Thin Disk ◽  
Piezoelectric Transducers ◽  
Parametric Models ◽  
Model Parameters ◽  
Linear Temperature Dependence ◽  
Linear Temperature ◽  
Wide Range

Piezoelectric ultrasonic transducers are used extensively in well logging and logging-while-drilling applications for pulse-echo operation. We present a method of modeling the operation of ultrasonic thin-disk piezoelectric transducers over a wide range of temperatures. The model is based on using Redwood's version of Mason's model of thin-disk transducers. Laboratory measurements in the oven of non-backed transducers in air are used to extract the Mason model parameters as a function of temperature. Derived parameters are frequency-thickness constant, dielectric constant, and thickness mode coupling coefficient. A fourth parameter, bulk density, is measured independently and assumed constant over temperature. Temperature dependence of frequency thickness constant and coupling coefficient are modeled as linear temperature coefficients. Temperature dependence of the dielectric constant must be specified as a table because of the non-linear temperature dependence of that parameter.

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