Anomalous magnetic behavior inBi2Sr2CaCu2O8+ysingle crystals near the superconducting-transition regime

1995 ◽  
Vol 52 (9) ◽  
pp. 6215-6218 ◽  
Author(s):  
A. K. Pradhan ◽  
S. B. Roy ◽  
P. Chaddah ◽  
C. Chen ◽  
B. M. Wanklyn
Keyword(s):  
Magnetic Behavior ◽  
Transition Regime ◽  
Superconducting Transition

SYNTHESIS, STRUCTURAL CHARACTERIZATION AND MAGNETIC BEHAVIOR OF RuSr2GdCu2O8/La0.67Sr0.33MnO3 COMPOSITES

2009 ◽  
Vol 23 (02) ◽  
pp. 137-146 ◽  
Author(s):  
L. T. CORREDOR ◽  
D. A. LANDÍNEZ TÉLLEZ ◽  
M. C. REYES O. ◽  
J. ROA-ROJAS ◽  
A. R. JURELO ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Structural Characterization ◽  
Exchange Bias ◽  
Magnetic Behavior ◽  
Superconducting Transition ◽  
Bias Effect ◽  
Magnetic Composites ◽  
Exchange Bias Effect ◽  
X Ray ◽  
Ferromagnetic Character

In this work we report the synthesis of RuSr 2 GdCu 2 O 8/ La 0.67 Sr 0.33 MnO 3 superconducting-magnetic composites with 50 vol.% of both RuSr 2 GdCu 2 O 8 and La 0.67 Sr 0.33 MnO 3 compounds. Structural characterization was performed by X-ray diffraction, which permitted us to establish the absence of other crystallographic phases and the non-reactive character of the compounds into the composite. Scanning electron microscopy showed the sub-micrometric size of the grains. Energy dispersive X-ray experiments confirmed chemical stability between RuSr 2 GdCu 2 O 8 and La 0.67 Sr 0.33 MnO 3 compounds in the composites. Resistivity measurements provided evidence of superconducting transition for the RuSr 2 GdCu 2 O 8 material, with TSC=39.2 K. Results of magnetization as a function of temperature corroborated the superconducting transition and showed the expected antiferromagnetic character of the Ru perovskite, with a Néel temperature TN=132.7 K. Systematic measurements of applied magnetic field up to 5 kOe were performed at these temperature regimes: TN < T < TC (with TC being the Curie temperature of the La 0.67 Sr 0.33 MnO 3 compound); TSC < T < TN; and T < TSC. Our results reveal the ferromagnetic character of the composites at the temperature regime TN < T < TC. The exchange bias effect was observed for weak applied fields (H < 1.5 kOe) at temperatures between TSC < T < TN. At the superconducting regime (T < TSC) weaker exchange bias is observed for low magnetic fields (H < 1 kOe). For strong magnetic fields (H > 2 kOe) the ferromagnetic character of the system is recovered.

scholarly journals Vortex phase transition and superconducting properties in quasi-two-dimensional k-(BEDT-TTF)2Cu[N(CN)2]Br organic superconductor

2018 ◽  
Vol 3 (1) ◽  
Author(s):  
H. El Ouaddi ◽  
A. Tirbiyine ◽  
A. Taoufik ◽  
Y. Ait Ahmed ◽  
F. Chiban ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Vortex Lattice ◽  
Magnetic Hysteresis ◽  
Magnetic Behavior ◽  
Organic Superconductor ◽  
Shielding Effect ◽  
Superconducting Transition ◽  
Critical Current Density Jc

We report investigations of the low temperature dc susceptibility and the magnetization on the layered organic superconductor k-(BEDT-TTF)2Cu[N(CN)2]Br near 80 K and the effect of disorder on the superconducting transition temperature Tc. The shielding effect (S) and the critical current density Jc were studied (with H parallel to the c axis of the crystal). Jc can be estimated by analysis of magnetic hysteresis measurement using the Bean model. For each temperature value, we observed two regimes in the critical current density Jc(H). Our results show that the magnetic properties of these compounds depend strongly on the cooling rate. The structural transformation which occurs at the vicinity of 80 K very strongly influences the physics of vortex lattice and the associated magnetic behavior. #organic_superconductor #critical_current #shielding_effect #magnetic_susceptibility #vortex_pinning

IMPACT OF Co AND Mo SUBSTITUTION AT Ru-SITE IN RuSr2Eu1.5Ce0.5Cu2O10-δ MAGNETO-SUPERCONDUCTOR

2006 ◽  
Vol 20 (29) ◽  
pp. 1901-1908 ◽  
Author(s):  
V. P. S. AWANA ◽  
H. KISHAN ◽  
E. TAKAYAMA-MUROMACHI ◽  
A. V. NARLIKAR
Keyword(s):  
Transition Temperature ◽  
Magnetic Transition ◽  
Magnetic Behavior ◽  
Temperature Data ◽  
Superconducting Transition ◽  
Antiferromagnetic Transition ◽  
Magnetic Transition Temperature ◽  
Pristine Sample ◽  
Transition Formula ◽  
Magnetization Data

Substitution of both Co and Mo at Ru -site in RuSr 2 Eu 1.5 Ce 0.5 Cu 2 O 10-δ system takes place iso-structurally in tetragonal structure (space group I4/mmm) with full solubility. The resistance versus temperature (R versus T) behavior of the pristine sample confirmed superconductivity [Formula: see text] around 25 K. The DC magnetization data (M versus T) for the same sample revealed magnetic transition (T mag ) at 140 K followed by superconducting transition [Formula: see text] at 32 K. With progressive Co substitution at Ru -site both [Formula: see text] and [Formula: see text] decrease monotonically and superconductivity is not observed for x ≥ 0.10 (10 at%). The magnetic behavior of materials with Co up to x = 0.2 preserves the magnetic structure of the parent RuSr 2 Eu 1.5 Ce 0.5 Cu 2 O 10-δ compound. For 0.8 ≥ x ≥ 0.2 a clear antiferromagnetic transition at TN=31 K is observed regardless of Co content. In the case of Mo -doped ruthenocuprates Ru 1-x Mo x Sr 2 Eu 1.5 Ce 0.5 Cu 2 O 10-δ, it has been found that the magnetic transition temperature decreases with x. The samples of x = 0.8 and 1.0 are found to have no magnetic or superconducting effects. The values of the superconducting transition temperature obtained from the resistivity versus temperature data increase by 4.5 and 7.0 K for x = 0.2 and 0.4 respectively, and then decrease by 17 K for x = 0.6. The observed variation of Tc with x in case of Mo has been explained in terms of a theory which combines the effects of weakening magnetic behavior and reducing carrier concentration in a phenomenological manner.

Microcalorimeters for X-Ray Spectroscopy

1988 ◽  
Vol 102 ◽  
pp. 41
Author(s):  
E. Silver ◽  
C. Hailey ◽  
S. Labov ◽  
N. Madden ◽  
D. Landis ◽  
...  
Keyword(s):  
High Resolution ◽  
High Efficiency ◽  
Thermal Response ◽  
Low Noise ◽  
High Resolution Spectroscopy ◽  
Superconducting Transition ◽  
Sapphire Substrates ◽  
Laboratory Plasmas ◽  
Adiabatic Demagnetization ◽  
Theoretical Predictions

The merits of microcalorimetry below 1°K for high resolution spectroscopy has become widely recognized on theoretical grounds. By combining the high efficiency, broadband spectral sensitivity of traditional photoelectric detectors with the high resolution capabilities characteristic of dispersive spectrometers, the microcalorimeter could potentially revolutionize spectroscopic measurements of astrophysical and laboratory plasmas. In actuality, however, the performance of prototype instruments has fallen short of theoretical predictions and practical detectors are still unavailable for use as laboratory and space-based instruments. These issues are currently being addressed by the new collaborative initiative between LLNL, LBL, U.C.I., U.C.B., and U.C.D.. Microcalorimeters of various types are being developed and tested at temperatures of 1.4, 0.3, and 0.1°K. These include monolithic devices made from NTD Germanium and composite configurations using sapphire substrates with temperature sensors fabricated from NTD Germanium, evaporative films of Germanium-Gold alloy, or material with superconducting transition edges. A new approache to low noise pulse counting electronics has been developed that allows the ultimate speed of the device to be determined solely by the detector thermal response and geometry. Our laboratory studies of the thermal and resistive properties of these and other candidate materials should enable us to characterize the pulse shape and subsequently predict the ultimate performance. We are building a compact adiabatic demagnetization refrigerator for conveniently reaching 0.1°K in the laboratory and for use in future satellite-borne missions. A description of this instrument together with results from our most recent experiments will be presented.

Lorentz electron microscopy of magnetic domains in rapidly solidified and annealed Pt-Co-B alloys

1991 ◽  
Vol 49 ◽  
pp. 784-785
Author(s):  
N. Qiu ◽  
J. E. Wittig
Keyword(s):  
Rapid Solidification ◽  
Ion Beam ◽  
Magnetic Behavior ◽  
High Coercivity ◽  
Magnetic Domains ◽  
Beam Angle ◽  
Tem Analysis ◽  
Intrinsic Coercivity ◽  
Hard Magnets ◽  
Rapidly Solidified

PtCo hard magnets have specialized applications owing to their relatively high coercivity combined with corrosion resistance and ductility. Increased intrinsic coercivity has been recently obtained by rapid solidification processing of PtCo alloys containing boron. After rapid solidification by double anvil splat quenching and subsequent annealing for 30 minutes at 650°C, an alloy with composition Pt42Co45B13 (at.%) exhibited intrinsic coercivity up to 14kOe. This represents a significant improvement compared to the average coercivities in conventional binary PtCo alloys of 5 to 8 kOe.Rapidly solidified specimens of Pt42Co45B13 (at.%) were annealed at 650°C and 800°C for 30 minutes. The magnetic behavior was characterized by measuring the coercive force (Hc). Samples for TEM analysis were mechanically thinned to 100 μm, dimpled to about 30 nm, and ion milled to electron transparency in a Gatan Duomill at 5 kV and 1 mA gun current. The incident ion beam angle was set at 15° and the samples were liquid nitrogen cooled during milling. These samples were analyzed with a Philips CM20T TEM/STEM operated at 200 kV.

Observation by HVEM of the martensite transformation and the superconducting transition in Nb3Sn

1988 ◽  
Vol 46 ◽  
pp. 788-789
Author(s):  
M. A. Kirk ◽  
M. C. Baker ◽  
B. J. Kestel ◽  
H. W. Weber
Keyword(s):  
Thin Films ◽  
Low Temperature ◽  
Superconducting State ◽  
Martensite Transformation ◽  
Sputter Deposition ◽  
Diffusion Reaction ◽  
Solute Diffusion ◽  
Superconducting Transition ◽  
Twin Boundaries ◽  
Martensite Structure

It is well known that a number of compound superconductors with the A15 structure undergo a martensite transformation when cooled to the superconducting state. Nb3Sn is one of those compounds that transforms, at least partially, from a cubic to tetragonal structure near 43 K. To our knowledge this transformation in Nb3Sn has not been studied by TEM. In fact, the only low temperature TEM study of an A15 material, V3Si, was performed by Goringe and Valdre over 20 years ago. They found the martensite structure in some foil areas at temperatures between 11 and 29 K, accompanied by faults that consisted of coherent twin boundaries on {110} planes. In pursuing our studies of irradiation defects in superconductors, we are the first to observe by TEM a similar martensite structure in Nb3Sn.Samples of Nb3Sn suitable for TEM studies have been produced by both a liquid solute diffusion reaction and by sputter deposition of thin films.

INCREASED RESISTANCE BELOW THE SUPERCONDUCTING TRANSITION IN DISCONTINUOUS FILMS OF (SN)x AND INDIUM

1978 ◽  
Vol 39 (C6) ◽  
pp. C6-448-C6-450 ◽  
Author(s):  
M. W. Young ◽  
J. M.D. Thomas ◽  
C. J. Adkins ◽  
J. W. Tate
Keyword(s):  
Superconducting Transition

STRANGE MAGNETIC BEHAVIOR IN THE LITHIUM-METHYLAMINE SYSTEM

1980 ◽  
Vol 41 (C8) ◽  
pp. C8-45-C8-48
Author(s):  
A. Stacy ◽  
D. C. Johnson ◽  
M. J. Sienko
Keyword(s):  
Magnetic Behavior

Transport Path in Hydrogenated Microcrystalline Silicon

2002 ◽  
Vol 715 ◽  
Author(s):  
N. Wyrsch ◽  
C. Droz ◽  
L. Feitknecht ◽  
J. Spitznagel ◽  
A. Shah
Keyword(s):  
Raman Spectroscopy ◽  
Volume Fraction ◽  
Conductivity Measurement ◽  
Dark Conductivity ◽  
Transition Regime ◽  
Conductivity Data ◽  
Crystalline Volume Fraction ◽  
Microcrystalline Silicon ◽  
Crystalline Fraction ◽  
Transport Path

AbstractUndoped microcrystalline silicon samples deposited in the transition regime between amorphous and microcrystalline growth have been investigated by dark conductivity measurement and Raman spectroscopy. From the latter, a semi-quantitative crystalline volume fraction Xc of the sample was deduced and correlated with dark conductivity data in order to reveal possible percolation controlled transport. No threshold was observed around the critical crystalline fraction value Xc of 33%, as reported previously, but a threshold in conductivity data was found at Xc≈50%. This threshold is interpreted here speculatively as being the result of postoxidation, and not constituting an actual percolation threshold.

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