HEAT-TREATMENT INFLUENCE ON THE MAGNETIC AND ELECTRIC PROPERTIES OF HIGH-TcYBa2Cu3O7−δ SUPERCONDUCTOR

1996 ◽  
Vol 10 (20) ◽  
pp. 955-961
Author(s):  
LAUREAN HOMORODEAN ◽  
IULIU POP ◽  
ION BURDOI
Keyword(s):  
Heat Treatment ◽  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Room Temperature ◽  
Liquid Nitrogen Temperature ◽  
Superconducting Phase ◽  
Superconducting Transition ◽  
Temperature Dependences ◽  
Magnetic And Electric Properties ◽  
Very High

The changes in the temperature dependences of the magnetic susceptibility and the electrical resistivity of a very-high-T c superconducting YBa 2 Cu 3 O 7−δ sample during the thermal cycling between the liquid-nitrogen temperature and the room temperature are studied. Some singularities corresponding to the superconducting transition, the possible existence of a super-high-temperature superconducting phase and the migration of the oxygen atoms in the Cu-O chains are emphasized on these dependencies.

scholarly journals Incompatibility of Published ac Magnetic Susceptibility of a Room Temperature Superconductor with Measured Raw Data

2021 ◽  
Author(s):  
J. E. Hirsch
Keyword(s):  
High Pressure ◽  
Magnetic Susceptibility ◽  
Room Temperature ◽  
Superconducting Transition ◽  
Ac Magnetic Susceptibility ◽  
Raw Data ◽  
Magnetic Susceptibility Data ◽  
Susceptibility Data ◽  
Room Temperature Superconductivity

Room temperature superconductivity has recently been reported for a carbonaceous sulfur hydride (CSH) under high pressure by Snider et al [1]. The paper reports sharp drops in magnetic susceptibility as a function of temperature for five different pressures, that are interpreted as signaling a superconducting transition. Here I question the validity and faithfulness of the magnetic susceptibility data presented in the paper by comparison with the measured raw data reported by two of the authors of ref. [2]. This invalidates the assertion of the paper [1] that the susceptibility measurements support the case for superconductivity in this compound.

PRESSURE EFFECT ON CONDUCTIVITY IN Au(dmit)2 LANGMUIR–BLODGETT FILMS

2002 ◽  
Vol 01 (05n06) ◽  
pp. 627-630 ◽  
Author(s):  
YASUHIRO F. MIURA ◽  
SHIN-ICHI MORITA ◽  
SHIN-HACHIRO SAITO ◽  
MICHIO SUGI ◽  
MASATO HEDO ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Room Temperature ◽  
Pressure Effect ◽  
Ambient Pressure ◽  
Superconducting Phase ◽  
Ac Magnetic Susceptibility ◽  
Temperature Resistance ◽  
Langmuir Blodgett ◽  
Langmuir Blodgett Films ◽  
Resistance Decrease

The resistance of the Langmuir–Blodgett films of ditetradecyldimethylammonium- Au(dmit) 2( 2C 14- Au(dmit) 2) salt has been measured under hydrostatic pressure up to 0.7 GPa. The room-temperature resistance decreases with increasing pressure, reaching a 0.6-times smaller value compared to that at ambient pressure. The film under the pressure shows a clear resistance decrease below 1.4 K on cooling, while that under ambient pressure shows a blunt decrease below 0.85 K and it turns to increase below 0.65 K. These results suggest the existence of the pressure-induced superconducting phase together with the earlier results of the ac magnetic susceptibility measurement.

ON THE STRUCTURAL, THERMAL, ELECTRICAL, AND MAGNETIC PROPERTIES OF AuSn

1963 ◽  
Vol 41 (12) ◽  
pp. 2252-2266 ◽  
Author(s):  
J.-P. Jan ◽  
W. B. Pearson ◽  
A. Kjekshus ◽  
S. B. Woods
Keyword(s):  
Thermal Conductivity ◽  
Magnetic Properties ◽  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Air Temperature ◽  
Homogeneity Range ◽  
Room Temperature ◽  
Lattice Constants ◽  
Conduction Electrons ◽  
Electrical And Magnetic Properties

The Au1−xSn phase has a homogeneity range within the limits 50.0 and 50.5 at.% Sn. The lattice constants and observed densities vary between the limits:[Formula: see text]The thermal conductivity, electrical resistivity, and absolute thermoelectric power of oriented single crystals of Au1−xSn have been measured between 2.5° K and room temperature. The results exhibit pronounced anisotropies. Measurements of the magnetic susceptibility between liquid air temperature and 650–750° K are also reported for three different Au1−xSn alloys.The various results are discussed, and some speculations are presented regarding the number of conduction electrons in AuSn.

Quenching and room-temperature annealing effects on the conductivity of underdoped HoBa2Cu3O7−δ

2018 ◽  
Vol 32 (01) ◽  
pp. 1750367 ◽  
Author(s):  
G. Ya. Khadzhai ◽  
R. V. Vovk ◽  
N. R. Vovk ◽  
Yu. I. Boiko ◽  
S. N. Kamchatnaya ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Single Crystals ◽  
Normal State ◽  
Room Temperature ◽  
Oxygen Vacancies ◽  
Phonon Scattering ◽  
Sample Volume ◽  
Residual Resistivity ◽  
Superconducting Transition ◽  
Annealing Effects

The effects of quenching from 600[Formula: see text]C and subsequent room-temperature annealing on the basal-plane electrical resistivity of underdoped HoBa2Cu3O[Formula: see text] single crystals are investigated. Regions with different superconducting transition temperatures, [Formula: see text], have been revealed in the sample after quenching and attributed to a non-uniform distribution of the labile oxygen in the sample volume. Room-temperature annealing has been revealed to lead to an increase of [Formula: see text] of all regions and a decrease of their number, attributed to the coalescence of clusters of oxygen vacancies. The temperature dependence of the resistance in the normal state is characterized by a decrease of the residual resistivity and the phonon scattering coefficient.

Electrical resistivity, magnetoresistance, and morphology of vapor-grown carbon fibers prepared in a mixture of benzene and Linz–Donawitz converter gas by floating catalyst method

1993 ◽  
Vol 8 (8) ◽  
pp. 1866-1874 ◽  
Author(s):  
Munehiro Ishioka ◽  
Toshihiko Okada ◽  
Kenji Matsubara ◽  
Michio Inagaki ◽  
Yoshihiro Hishiyama
Keyword(s):  
Heat Treatment ◽  
Electrical Resistivity ◽  
Carbon Fibers ◽  
Treatment Time ◽  
Liquid Nitrogen Temperature ◽  
Treatment Temperature ◽  
Heat Treated ◽  
Cobalt Acetylacetonate ◽  
Converter Gas ◽  
Transition Heat

Vapor-grown carbon fibers (VGCF's) were prepared in a mixture of benzene and Linz–Donawitz converter gas using floating catalytic seeds derived from ferrocene, cobalt acetylacetonate, and thiophene. The diameters of the fibers thus grown were in the range of 2–7 μm. The fibers were heat-treated in argon atmosphere at temperatures between 1700 and 3000 °C. The electrical resistivity at room temperature and magnetoresistance at liquid nitrogen temperature were measured for the as-grown and heat-treated fibers, and morphology of the heat-treated fibers was observed with a scanning electron microscope. The electrical resistivity was nearly similar to that obtained for VGCF's prepared on a substrate in a mixture of benzene and hydrogen. The size effects on the resistivity and magnetoresistance were observed. The magnetoresistance was also found to depend on the heat-treatment time. The magnetoresistance results showed that a transition heat-treatment temperature for the magnetoresistance change from negative to positive was between 2200 and 2300 °C, indicating the graphitizable nature of the present fiber. A characteristic polygonal appearance was observed for the fibers heat-treated above 2500 °C.

Low-temperature electrical resistivity and magnetic susceptibility of dilute Mg–Ce alloys

1970 ◽  
Vol 48 (11) ◽  
pp. 1283-1287 ◽  
Author(s):  
F. T. Hedgcock ◽  
B. Petrie
Keyword(s):  
Electrical Resistivity ◽  
Magnetic Susceptibility ◽  
Low Temperature ◽  
Fermi Level ◽  
Magnesium Alloys ◽  
Conduction Electron ◽  
Room Temperature ◽  
Impurity Scattering ◽  
Cerium Ion ◽  
Normal Potential

The electrical resistivity of a series of magnesium alloys containing from 300 to 1041 parts per million of gadolinium has been measured from 4.2 °K to room temperature. No low-temperature anomalies have been observed and it is found that Matthiessen's rule is obeyed extremely well over the whole temperature range studied. The electrical resistivity and magnetic susceptibility measurements indicate that the cerium ion in magnesium is in a triply ionized state, and that the contribution to the resistivity can be almost totally accounted for by assuming normal potential impurity scattering. This suggests that the f level of cerium in magnesium lies well below the fermi level of magnesium and that there is very little s–f mixing between the f level of cerium of the conduction electron states of magnesium.

scholarly journals Superconductivity in room-temperature stable electride and high-pressure phases of alkali metals

2015 ◽  
Vol 373 (2037) ◽  
pp. 20140450 ◽  
Author(s):  
Hideo Hosono ◽  
Sung-Wng Kim ◽  
Satoru Matsuishi ◽  
Shigeki Tanaka ◽  
Atsushi Miyake ◽  
...  
Keyword(s):  
High Pressure ◽  
Fermi Energy ◽  
Electronic Structures ◽  
Alkali Metals ◽  
Alkaline Earth ◽  
Room Temperature ◽  
Ambient Pressure ◽  
Superconducting Phase ◽  
Alkaline Earth Metals ◽  
Superconducting Transition

S-band metals such as alkali and alkaline earth metals do not undergo a superconducting transition (SCT) at ambient pressure, but their high-pressure phases do. By contrast, room-temperature stable electride [Ca 24 Al 28 O 64 ] 4+ ⋅4e − (C12A7:e − ) in which anionic electrons in the crystallographic sub-nanometer-size cages have high s-character exhibits SCT at 0.2–0.4 K at ambient pressure. In this paper, we report that crystal and electronic structures of C12A7:e − are close to those of the high-pressure superconducting phase of alkali and alkaline earth metals and the SCT of both materials is induced when electron nature at Fermi energy ( E F ) switches from s- to sd-hybridized state.

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