scholarly journals Quasiperiodic transition to chaos in Ge; and magnetic susceptibility of high- Tc superconductors

1990 ◽  
Author(s):  
Youngtae Kim
Keyword(s):  
Magnetic Susceptibility ◽  
High Tc Superconductors ◽  
High Tc ◽  
Transition To Chaos

Structural and Magnetic Characteristics of (Eu1-xGax) Ba2Cu3O7-δ High-Tc Superconductors

1997 ◽  
Vol 11 (13) ◽  
pp. 593-597 ◽  
Author(s):  
Iuliu Pop ◽  
Radu Redac ◽  
Gheorghe Borodi ◽  
Virgil Ioncu
Keyword(s):  
Magnetic Susceptibility ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Tetragonal Structure ◽  
Magnetic Characteristics ◽  
High Tc Superconductors ◽  
High Tc ◽  
Gallium Concentration ◽  
Paramagnetic Region ◽  
Diamagnetic Transition

The high-T c ( Eu 1-x Ga x) Ba 2 Cu 3 O 7-δ superconductors with x=0, 0.01, 0.02, 0.03, 0.06 and 0.09 were synthesized by a ceramic technique. The gallium concentration dependence of the lattice parameters was determined. A transition from orthorhombic toward tetragonal structure was relevated for the most gallium concentrated sample. The temperature dependence of the magnetic susceptibility pointed out the diamagnetic transition at 78 and 80 K. In the paramagnetic region the magnetic susceptibility exhibits anomal temperature dependence.

43Ca NMR Study of Bismuth-Based High-Tc Superconductors

1994 ◽  
Vol 49 (1-2) ◽  
pp. 373-378 ◽  
Author(s):  
A. Trokiner ◽  
L. Le Noc ◽  
A. Yakubovskii ◽  
K.N. Mykhalyov ◽  
S.V. Verkhovskii
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Electronic Properties ◽  
High Tc Superconductors ◽  
High Tc ◽  
Structural Assignment ◽  
Bismuth Compounds ◽  
Nmr Study

Abstract As a first step of a study of the electronic properties of CuO2 planes by probing calcium nuclei in the bismuth-based high-Tc materials we report here the structural assignment of Ca NMR lines measured in 43Ca-enriched samples of n = 2 ((Bi,Pb)2Sr2CaCu2O8+x) and n = 3 ((Bi,Pb)2Sr2-Ca2Cu3O10+x) bismuth compounds. Powdered samples were investigated as well as oriented pow­ ders, achieved by uniaxial alignment of the grains in a 7T magnetic field. For the main calcium site (Ca between two CuO2 planes), we could determine the quadrupolar as well as the shift tensors. The results indicate that, in the same way as yttrium nuclei in YBaCuO, calcium nuclei are sensitive to the magnetic susceptibility of the metallic CuO2 planes.

MAGNETIC PROPERTIES OF Yb1-xGaxBa2Cu3O7-δ HIGH TC SUPERCONDUCTORS

2008 ◽  
Vol 22 (21) ◽  
pp. 3677-3682
Author(s):  
IULIU POP ◽  
CARMEN SBÂRCIOG ◽  
OVIDIU POP
Keyword(s):  
Magnetic Susceptibility ◽  
Curie Constant ◽  
Thermal Variation ◽  
High Tc Superconductors ◽  
High Tc ◽  
Static Magnetic Susceptibility ◽  
X Ray ◽  
Paramagnetic Region ◽  
Valence States ◽  
Superconducting Compounds

The thermal variation of the static magnetic susceptibility, for the Yb 1-x Ga x Ba 2 Cu 3 O 7-δ, x = 0.00; 0.01; 0.02; 0.03; 0.06 oxidic high TC superconductors was investigated. In the paramagnetic region, the reciprocal magnetic susceptibility temperature dependence is nonlinear, obeying the hyperbolic Neel law, valid for the ferromagnetic collinear magnetic structure. The effective magnetic moment value determined from the Curie constant is a giant one, suggesting the existence of Cu 3+ and Yb 6+ valence states in high TC superconducting compounds. The structural X-ray investigation revealed a homogeneous orthorhombic crystalline structure in Yb 1-x Ga x Ba 2 Cu 3 O 7-δ superconducting compounds.

The many faces of STEM in materials science

1991 ◽  
Vol 49 ◽  
pp. 440-441
Author(s):  
John Silcox
Keyword(s):  
Materials Science ◽  
Auger Spectroscopy ◽  
Dark Field ◽  
High Tc Superconductors ◽  
High Tc ◽  
Acoustic Environment ◽  
Electromagnetic Vibration ◽  
The Many ◽  
Serial Mode

Determination of the microstructure and microchemistry of small features often provides the insight needed for the understanding of processes in real materials. In many cases, it is not adequate to use microscopy alone. Microdiffraction and microspectroscopic information such as EELS, X-ray microprobe analysis and Auger spectroscopy can all contribute vital parts of the picture. For a number of reasons, dedicated STEM offers considerable promise as a quantitative instrument. In this paper, we review progress towards effective quantitative use of STEM with illustrations drawn from studies of high Tc superconductors, compound semiconductors and metallization of H-terminated silicon.Intrinsically, STEM is a quantitative instrument. Images are acquired directly by detectors in serial mode which is particularly convenient for digital image acquisition, control and display. The VG HB501A at Cornell has been installed in a particularly stable electromagnetic, vibration and acoustic environment. Care has been paid to achieving UHV conditions (i.e., 10-10 Torr). Finally, it has been interfaced with a VAX 3200 work station by Kirkland. This permits, for example, the acquisition of bright field (or energy loss) images and dark field images simultaneously as quantitative arrays in perfect registration.

Crystal chemistry of high-Tc superconductors

1990 ◽  
Vol 48 (4) ◽  
pp. 1118-1119
Author(s):  
Maryvonne Hervieu
Keyword(s):  
Oxygen Deficiency ◽  
Large Family ◽  
Copper Oxides ◽  
High Tc Superconductors ◽  
High Tc ◽  
Single Mechanism ◽  
Square Planar ◽  
History Of ◽  
Bismuth Cuprates ◽  
New Compounds

Four years after the discovery of superconductivity at high temperature in the Ba-La-Cu-O system, more than thirty new compounds have been synthesized, which can be classified in six series of copper oxides: La2CuO4 - type oxides, bismuth cuprates, YBa2Cu3O7 family, thallium cuprates, lead cuprates and Nd2CuO4 - type oxides. Despite their quite different specific natures, close relationships allow their structures to be simply described through a single mechanism. The fifth first families can indeed be described as intergrowths of multiple oxygen deficient perovskite slabs with multiple rock salt-type slabs, according to the representation [ACuO3-x]m [AO]n.The n and m values are integer in the parent structures, n varying from 0 to 3 and m from 1 to 4; every member of this large family can thus be symbolized by [m,n]. The oxygen deficient character of the perovskite slabs involves the existence or the co-existence of several types of copper environment: octahedral, pyramidal and square planar.Both mechanisms, oxygen deficiency and intergrowth, are well known to give rise easily to nonstoichiometry phenomena. Numerous and various phenomena have actually been characterized in these cuprates, strongly depending on the thermal history of the samples.

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