Nuclear magnetic resonance study of superconductivity in strontium-doped lanthanum copper oxides

Miscellaneous · Fri Jan 01 00:00:00 EST 1993

OSTI ID:7071603

Kennard, M A

The goal of this research is to examine a series of copper-oxide based superconductors, La[sub 2[minus]x]Sr[sub x]CuO[sub 4] for 0.10 [<=] x [<=] 0.20, using nuclear magnetic resonance and nuclear quadrupole resonance spectroscopies. Structural and chemical properties of the materials were confirmed by TGA, and powder x-ray diffraction. For each composition, two distinct sites correlates well with the amount of strontium added. The temperature dependence of the [sup 63z]Cu Knight shift of the two sites in La[sub 1.84]Sr[sub 0.16]CuO[sub 4] are identical, indicating that both are in the superconducting phase. Comparison was made between the [sup 63]Cu Knight shifts of La[sub 1.90]Sr[sub 0.10]CuO[sub 4], La[sub 1.84]Sr[sub 0.16]CuO[sub 4] and La[sub 1.80]Sr[sub 0.20]CuO[sub 4] in the normal and superconducting states. These results, combined with magnetic susceptibility measurements, allow the separation of the carrier spin and orbital contributions to the susceptibility. At temperatures just above the superconducting transition, the conduction electron spin susceptibility increases dramatically with strontium doping. The Knight shift of all three compositions converge to the same value of K(0) = 0.17 [+-] 0.04 below T[sub c]. The temperature dependence of the Knight shift at low temperature suggest that the spine susceptibility is zero and the superconducting state is a spin singlet. Differences in the temperature dependence of the spin susceptibility clearly show that under doped, optimally doped and over doped samples are intrinsic superconductors. This work has revealed that the microscopic environment around copper is much more complex than was previously believed.

• Research Organization: Northwestern Univ., Chicago, IL (United States)
• OSTI ID: 7071603
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COPPER OXIDES
NUCLEAR MAGNETIC RESONANCE
NUCLEAR QUADRUPOLE RESONANCE
SUPERCONDUCTIVITY
DOPED MATERIALS
INTERMETALLIC COMPOUNDS
KNIGHT SHIFT
LANTHANUM OXIDES
MAGNETIC SUSCEPTIBILITY
STRONTIUM OXIDES
TEMPERATURE DEPENDENCE
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
CHALCOGENIDES
COPPER COMPOUNDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
LANTHANUM COMPOUNDS
MAGNETIC PROPERTIES
MAGNETIC RESONANCE
MATERIALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
RESONANCE
STRONTIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360207* - Ceramics
Cermets
&amp; Refractories- Superconducting Properties- (1992-)