Study of superconductivity and magnetism by pressurization and hydrogenation

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1981

OSTI ID:6203545

Huang, S Z

In a general attempt to understand the occurrence of high temperature superconductors and to search for high temperature superconductors, the hydrogenation and high pressure techniques were employed for the study of compounds with known high superconducting transition temperature T/sub c/ and those possibly with novel superconducting interaction. The high T/sub c/ vanadium-based A15 compounds, the ternary Eu molybdenum chalcogenides, and the itinerant ferromagnets ZrZn/sub 2/ and TiBe/sub 2-x/Cu/sub x/ have been chosen for such an investigation. The results are summarized as follows: (1) the high T/sub c/V-based A15 superconductors: hydrogenation has been found to degrade the T/sub c/ of these compounds, similar to radiation damage. This is attributed to the reduction in the electron-lifetime rather than the reduction in the energy gap anisotropy due to the accompanying increase of defects. Our high pressure measurements show that the defect-induced volume expansion is not responsible for the T/sub c/-suppression. Our experimental and theoretical data also demonstrate the importance of metastability in the formation of defects in high T/sub c/ compounds. The high T/sub c/ of Nb/sub 3/Al and Nb/sub 3/Ge with low electron density of states at the Fermi level can thus be understood. (2) Ternaries (Eu/sub 1-x/Sn/sub x/)/sub 1.2/Mo/sub 6/(S/sub 1-y/Se/sub y/)/sub 8/: non-bulk superconductivity was induced in Eu/sub 1.2/Mo/sub 6/S/sub 8/ abruptly at approx. 7 kbar with an onset temperature approx. 11 K but not in its isoelectronic counterpart Eu/sub 1.2/Mo/sub 6/Se/sub 8/. The unusual superconductivity observed in Eu/sub 1.2/Mo/sub 6/S/sub 8/ under pressure is tentatively ascribed to interface superconductivity through the exciton mechanism or negative U-center interaction. The results of our high pressure measurements on (Eu/sub 1-x/Sn/sub x/)/sub 1.2/Mo/sub 6/(S/sub 1-y/Se/sub y/)/sub 8/ consistent with such a conjecture.

• Research Organization: Houston Univ., TX (USA)
• OSTI ID: 6203545
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360104* -- Metals & Alloys-- Physical Properties
656102 -- Solid State Physics-- Superconductivity-- Acoustic
Electronic
Magnetic
Optical
& Thermal Phenomena-- (-1987)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALLOYS
CHEMICAL REACTIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
EUROPIUM ALLOYS
EUROPIUM BASE ALLOYS
HYDROGENATION
MAGNETISM
PHYSICAL PROPERTIES
PRESSURE DEPENDENCE
RARE EARTH ALLOYS
SUPERCONDUCTIVITY
THERMODYNAMIC PROPERTIES
TITANIUM ALLOYS
TITANIUM BASE ALLOYS
TRANSITION TEMPERATURE
VANADIUM ALLOYS
VANADIUM BASE ALLOYS
ZIRCONIUM ALLOYS
ZIRCONIUM BASE ALLOYS