Elastic studies of phase transitions in Bechgaard salts, YBaCuO[sub 7[minus][delta]] high-[Tc] superconductor and fullerene
Using a vibrating reed technique, the authors have studied the sound velocity of several materials which undergo electronic and structural phase transitions. The sound velocity in the highly anisotropic (TMTSF)-organic conductors were studied at low temperature and in high magnetic field to investigate the properties associated with the cascade of magnetic field-induced-spin-density-wave (FISDW) transitions. The dramatical response of the elastic constant at the Peierls-like transitions reflects a large stress dependence of the system's critical temperatures and fields. The characteristically different behaviors of the sound velocity in different temperature regions enables one to distinguish a low temperature insulating state from the higher temperature reentrant metallic state. Fast quantum oscillations are observed with a greatly enhanced amplitude accompanied by higher harmonic content and a phase shift when crossing the reentrant phase line, indicating coupling between the FISDW with the fast oscillations. Studies on the high-temperature superconductor YBaCu[sub 3]O[sub 7[minus][sigma]] reveals anomalously large softening in the elastic constant at the superconducting transition temperature. Hardening of the lattice below Tc indicates strong dependence of the transition temperature on the second derivative of the stress. The profound attenuation peaks at 135K and 220K suggest subtle structure transformations in the lattice. Probing the flux dynamics in YBaCu[sub 3]O[sub 7[minus][sigma]] with the vibrating reed, the authors observed low level flux dissipation at very low field. The critical current associated with the flux line pinning is determined to be 0.5[times]10[sup 6]A/cm[sup 2]. Sound velocity and attenuation studies on C[sub 60] fullerene found an 8% jump in the elastic constant at the first order orientational ordering transition. A frequency dependent attenuation peak at 160K for 20kHz probing frequency was discovered.
- Research Organization:
- Pennsylvania Univ., Philadelphia, PA (United States)
- OSTI ID:
- 7166670
- Country of Publication:
- United States
- Language:
- English
Similar Records
Studies on highly anisotropic conductors and superconductors in high magnetic fields and low temperatures
Superconductivity and magnetic-field-induced spin-density waves
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Cermets
& Refractories-- Structure & Phase Studies
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360602 -- Other Materials-- Structure & Phase Studies
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ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CARBON
COPPER COMPOUNDS
CUPRATES
ELEMENTS
ENERGY-LEVEL TRANSITIONS
FULLERENES
HIGH-TC SUPERCONDUCTORS
NONMETALS
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS