scholarly journals Apparatus for nonresonant rf power absorption studies in high Tc superconductors and CMR materials using rf oscillators

2005 ◽  
Vol 76 (2) ◽  
pp. 023905 ◽  
Author(s):  
S. Sarangi ◽  
S. V. Bhat
Keyword(s):  
Rf Power ◽  
High Tc Superconductors ◽  
Power Absorption ◽  
High Tc ◽  
Absorption Studies ◽  
Rf Oscillators

MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS VI—NON-RESONANT MICROWAVE ABSORPTION IN ULTRA-THIN Bi-Sr-Ca-Cu-O FILMS—

1992 ◽  
Vol 06 (05) ◽  
pp. 265-272 ◽  
Author(s):  
K. SUGAWARA ◽  
T. SUGIMOTO ◽  
D.J. BAAR ◽  
Y. SHIOHARA ◽  
S. TANAKA
Keyword(s):  
Magnetic Field ◽  
Microwave Absorption ◽  
Signal Intensity ◽  
Critical Magnetic Field ◽  
High Tc Superconductors ◽  
Temperature Relation ◽  
High Tc ◽  
Absorption Studies ◽  
Increasing Temperature ◽  
Mgo Substrate

Non-resonant microwave absorption (NRMA) studies have been done for Bi-Sr-Ca-Cu-O (BSCCO) films with thicknesses of 30 Å and 15 Å fabricated on MgO substrate by MOCVD. For the latter two kinds of samples have been fabricated: BSCCO/MgO and BiOx/BSCCO/MgO . NRMA signals have been detected up to about 70–75 K for all the samples. The lower critical magnetic field H c1 * of the 30 Å film was severely increased by the application of a magnetic field of several kGauss, whereas it is almost unaffected in the case of 15 Å films. H c1 * increases but the signal intensity decreases with increasing temperature for all the 30 Å and 15 Å samples. The temperature dependence of the intensity is quite different from that of thicker films (100 Å and 350 Å), in which the intensity vs. temperature relation has a peak (or peaks) at particular temperature(s).

MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS I—LOW-FIELD MICROWAVE ABSORPTION IN A BiSrCaCuO THIN FILM DEPOSITED BY MOCVD

1991 ◽  
Vol 05 (09) ◽  
pp. 667-674 ◽  
Author(s):  
K. SUGAWARA ◽  
T. SUGIMOTO ◽  
K. YASUIKE ◽  
D.J. BAAR ◽  
Y. SHIOHARA ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Film ◽  
Microwave Absorption ◽  
Applied Field ◽  
Film Plane ◽  
Experimental Results ◽  
High Tc Superconductors ◽  
High Tc ◽  
Low Field ◽  
Absorption Studies

Non-resonant microwave absorption as a function of temperature and magnetic field has been studied in a Bi-Sr-Ca-Cu-O film prepared by MOCVD. A maximum in the absorption as a function of temperature was observed at approximately 60 K. An average Josephson loop diameter of about 0.9~1.5 microns was inferred from the experimental results. The absorption was found to depend on the angle of the film plane relative to the applied field.

MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS VII — ESR OF DPPH COATED ON A THIN BiSrCaCuO FILM FABRICATED ON MgO(100) SUBSTRATE

1992 ◽  
Vol 06 (11) ◽  
pp. 675-682
Author(s):  
K. SUGAWARA ◽  
T. SUGIMOTO ◽  
Y. SHIOHARA ◽  
S. TANAKA
Keyword(s):  
Magnetic Field ◽  
Critical Current Density ◽  
Temperature Dependence ◽  
Microwave Absorption ◽  
Current Density ◽  
Applied Magnetic Field ◽  
High Tc Superconductors ◽  
High Tc ◽  
Absorption Studies ◽  
Mpmg Method

ESR of DPPH coated on a Bi-Sr-Ca-Cu-O (BSCCO) film (350 Å thick) fabricated on MgO(100) substrate by MOCVD was studied. Temperature dependence of the ESR peak-to-peak linewidth, ΔH pp , and the effect of applied magnetic field on ΔH pp have been studied below about 100 K. The results were compared with those of ESR of DPPH coated on ceramic Y-Ba-Cu-O samples (powder and bulk) made by the MPMG method. The DPPH ESR for the BSCCO film revealed that ΔH pp was independent of applied magnetic field up to about 9 kG. In addition, no similarity between the temperature dependence of the excess ESR linewidth of the DPPH and that of critical current density was found for the BSCCO film. These results for the BSCCO film are different from those for the MPMG YBCO samples.

MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS VIII — ESR OF DPPH COATED ON BiSrCaCuO FILMS FABRICATED ON MgO (100) SUBSTRATES

1992 ◽  
Vol 06 (14) ◽  
pp. 879-889
Author(s):  
K. SUGAWARA ◽  
S. TANAKA
Keyword(s):  
Magnetic Field ◽  
Film Thickness ◽  
Temperature Dependence ◽  
Applied Magnetic Field ◽  
Zero Field ◽  
Magnetic Field Effects ◽  
High Tc Superconductors ◽  
Thick Sample ◽  
High Tc ◽  
Absorption Studies

ESR of DPPH coated on Bi - Sr - Ca - Cu - O films fabricated on MgO (100) substrates by MOCVD have been studied for samples with different thicknesses, 1000 Å and 100 Å. Temperature dependence of the ESR peak-to-peak linewidth, ΔH pp , revealed that ΔH pp , increases with film thickness. The excess ESR linewidth, δ (ΔH pp ) was also analyzed in terms of (1-t)α, with t=T/T c , giving for example α=4±1 for the 1000 Å thick sample. The ESR lineshapes were distorted by rotating the samples in applied magnetic fields. Severe distortion was found for the 1000 Å sample below about 30 K, but the distortion almost disappears at temperatures above 30 K. The applied magnetic field effects were also examined in both field-cooled and zero-field-cooled cases.

MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS V-ANOMALOUS BEHAVIOR OF LOW MAGNETIC FIELD MICROWAVE ABSORPTION IN AN ULTRA-THIN Bi-Sr-Ca-Cu-O FILM

1991 ◽  
Vol 05 (30) ◽  
pp. 1981-1987 ◽  
Author(s):  
K. SUGAWARA ◽  
T. SUGIMOTO ◽  
D.J. BAAR ◽  
Y. SHIOHARA ◽  
S. TANAKA
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
Microwave Absorption ◽  
Anomalous Behavior ◽  
High Tc Superconductors ◽  
High Tc ◽  
Absorption Studies ◽  
Signal Changes ◽  
Low Magnetic Field ◽  
Mgo Substrate

Non-resonant microwave absorption (NRMA) studies have been done on a 100 Å thick Bi-Sr-Ca-Cu-O film fabricated on MgO substrate by MOCVD. Temperature dependence of NRMA intensity reveals that the intensity becomes maximum at around 30 K, 40 K and 55 K, and minimum at around 35 K and 50 K. The sign (or phase) of the signal changes by passing through these intensity minimum temperatures. Furthermore, the linewidths of the NRMA signals anomalously increase in the vicinity of these temperatures.

X-ray absorption studies of La2-x(Ba,Sr)xCuO4 high-Tc superconductors

1993 ◽  
Vol 209 (4) ◽  
pp. 373-380 ◽  
Author(s):  
M.J. Akhtar ◽  
Z.N. Akhtar ◽  
C.R.A. Catlow
Keyword(s):  
High Tc Superconductors ◽  
High Tc ◽  
X Ray ◽  
Absorption Studies ◽  
X Ray Absorption

MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS III: Electron Spin Resonance Studies of Y2Ba1Cu1O5 and Gd2Ba1Cu1O5

1991 ◽  
Vol 05 (13) ◽  
pp. 895-901 ◽  
Author(s):  
K. SUGAWARA ◽  
D. J. BAAR ◽  
Y. SHIOHARA ◽  
S. TANAKA
Keyword(s):  
Electron Spin Resonance ◽  
Microwave Absorption ◽  
Electron Spin ◽  
Room Temperature ◽  
Magnetic Ordering ◽  
High Tc Superconductors ◽  
Néel Temperature ◽  
High Tc ◽  
Spin Resonance ◽  
Absorption Studies

The ESR of Cu 2+ and Gd 3+ ion in Y 2 Ba 1 Cu 1 O 5 and Gd 2 Ba 1 Cu 1 O 5 has been studied at temperatures from 4 K to room temperature. Particular emphasis has been paid to the ESR linewidths (∆H PP ) and g-values of the ions. The ∆H PP and g-values for Y 2 Ba 1 Cu 1 O 5 were found to have anomalous increments near 15 K, close to the Néel temperature of Y 2 Ba 1 Cu 1 O 5. Similarly, ∆H PP for Gd 2 Ba 1 Cu 1 O 5 had peaks near 12 K. Our analysis reveals that the ESR signal from Gd 2 Ba 1 Cu 1 O 5 is dominated by the Gd 3+ ESR. However, the magnetic ordering may be caused by both Gd-Gd and Gd-Cu interactions.

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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