Superconducting Transition in к-Bedt-TTF Salts Under Magnetic Field

1992 ◽  
Vol 247 ◽  
Author(s):  
Hiroshi Ito ◽  
Yoshio Nogami ◽  
Masashi Watanabe ◽  
Takehiko Ishiguro ◽  
Tokutaro Komatsu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Organic Superconductors ◽  
Superconducting Transition ◽  
Isotope Substitution ◽  
Ginzburg Landau ◽  
Magnetization Measurements ◽  
Coherence Lengths

ABSTRACTThe superconducting transition under magnetic field for organic superconductors к-(BEDT-TTF)2 Cu(NCS)2 and к-(BEDT-TTFh)2 Cu[N(CN)2]Br has been analyzed by employing fluctuation renormal-ization theory. From magnetization measurements the interlayer and intralayer Ginzburg-Landau coherence lengths are determined. The effect of the isotope substitution to BEDT-TTF molecules has been studied. The result for resistive measurements is also described.

scholarly journals Microscopic Observation of π Spin Polarization by d Localized Spin in λ Type BETS Based Organic Superconductors

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1055
Author(s):  
Ko-ichi Hiraki ◽  
Toshihiro Takahashi ◽  
Hiroshi Akiba ◽  
Yutaka Nishio ◽  
Biao Zhou
Keyword(s):  
Magnetic Field ◽  
Low Temperature ◽  
Spin Polarization ◽  
Organic Superconductors ◽  
Exchange Field ◽  
Superconducting Transition ◽  
Nmr Spectrum ◽  
Fe Sites ◽  
Low Magnetic Field ◽  
Ga Doping

In this study, 77Se NMR measurements were carried out to detect the π spin polarization of the organic BETS (BETS = Bis(ethylenedithio)tetraselenafulvalene) molecule of the field induced superconductor, λ-(BETS)2Fe1−xGaxCl4, which shows a superconducting transition at relatively low magnetic field compared to the non-doped λ-(BETS)2FeCl4. From the analysis of the NMR spectrum at low temperature, it was clarified that the exchange interaction between π and 3d spins in the Ga doping system is smaller than that in the Fe salt. It is also clarified that the conduction π spins feel the “averaged” exchange field from the localized 3d spins at the dilute Fe sites.

MAGNETIC FIELD DEPENDENCE OF ENTROPY AND SPECIFIC HEAT OF YBa2Cu3O7-δ SUPERCONDUCTORS

2012 ◽  
Vol 26 (02) ◽  
pp. 1250051 ◽  
Author(s):  
B. KALTA ◽  
P. NAYAK ◽  
K. K. NANDA
Keyword(s):  
Magnetic Field ◽  
Specific Heat ◽  
Magnetic Field Dependence ◽  
Landau Theory ◽  
Thermodynamic Quantities ◽  
Type Ii ◽  
Large Reduction ◽  
Superconducting Transition ◽  
Ginzburg Landau ◽  
Type Ii Superconductors

The change in thermodynamic quantities (e.g., entropy, specific heat etc.) by the application of magnetic field in the case of the high-Tc superconductor YBCO system is examined phenomenological by the Ginzburg–Landau theory of anisotropic type-II superconductors. An expression for the change in the entropy (ΔS) and change in specific heat (ΔC) in a magnetic field for any general orientation of an applied magnetic field Ba with respect to the crystallographic c-axis is obtained. The observed large reduction of specific heat anomaly just below the superconducting transition and the observed variation of entropy with magnetic field are explained quantitatively.

Resistive superconducting transition of ?-type BEDT-TTF organic superconductors in a magnetic field

1994 ◽  
Vol 7 (3) ◽  
pp. 667-669 ◽  
Author(s):  
Hiroshi Ito ◽  
Takehiko Ishiguro ◽  
Tokutaro Komatsu ◽  
Nozomu Matsukawa ◽  
Gunzi Saito ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Organic Superconductors ◽  
Superconducting Transition

scholarly journals Синтез тонких пленок ниобия на кремнии и исследование их сверхпроводящих свойств в области размерного кроссовера

2021 ◽  
Vol 91 (2) ◽  
pp. 275
Author(s):  
И.В. Янилкин ◽  
А.И. Гумаров ◽  
А.М. Рогов ◽  
Р.В. Юсупов ◽  
Л.Р. Тагиров
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Electrical Resistance ◽  
Three Dimensional ◽  
Specific Effect ◽  
Two Dimensional ◽  
Superconducting Transition ◽  
Conduction Electrons ◽  
The Magnetic Field ◽  
Coherence Lengths

Niobium films of 4–100 nm thickness were synthesized on a silicon substrate under ultrahigh vacuum conditions. Measurements of electrical resistance showed a high temperature of the superconducting transition Tc, in the range of 4.7–9.1 K, and extremely small transition widths ΔTc in the range of 260–11 mK. The dependences of Tc and ΔTc on the magnetic field were studied, and superconducting coherence lengths and mean free paths of the conduction electrons were determined for different thicknesses of the synthesized films. A specific effect of the magnetic field on ΔTc was found, which reveals a transition from three-dimensional to two-dimensional superconductivity at thicknesses below 10 nm. The dependences of Tc and ΔTc on the films thickness and the magnitude of the magnetic field are discussed in the framework of existing concepts of superconductivity in thin films of superconducting metals.

Fluctuating Diamagnetism in the Critical Region of the Superconducting Transition in Lead Nanoparticles

2006 ◽  
Vol 47 ◽  
pp. 98-103
Author(s):  
E. Bernardi ◽  
A. Lascialfari ◽  
A. Rigamonti ◽  
L. Romanò ◽  
Vincenzo Iannotti ◽  
...  
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Superconducting State ◽  
Critical Region ◽  
Coherence Length ◽  
Fluctuation Theory ◽  
Superconducting Transition ◽  
Ginzburg Landau ◽  
Magnetization Measurements ◽  
First Order

High resolution SQUID magnetization measurements in Lead nanoparticles are presented and discussed in terms of the fluctuation-related diamagnetism in the critical region of the transition to the superconducting state, where the first-order fluctuation theory breaks down. Exact expressions of the magnetization are derived from the Ginzburg-Landau functional in zerodimensional condition (i.e. for grain size lesser than the coherence length) and are used to achieve insights on the properties of the critical fluctuating diamagnetism.

Optimization of Sample Holder Materials for Sensitive Magnetometry Measurements at Low Temperatures

2004 ◽  
Vol 825 ◽  
Author(s):  
I. Bossi ◽  
N.R. Dilley ◽  
J. R. O'Brien ◽  
S. Spagna
Keyword(s):  
Magnetic Field ◽  
Low Temperatures ◽  
Magnetic Response ◽  
Sample Holder ◽  
Magnetization Measurements ◽  
Temperature Range ◽  
Paramagnetic Impurities ◽  
Fused Quartz

AbstractMagnetization measurements were performed as a function of magnetic field H and temperature T on samples of nine different materials including clear fused quartz, cartridge brass, G-10 glass-reinforced epoxy, acetal homopolymer, glass-filled acetal, phenolic, and other plastics. A small yet distinct amount of ferromagnetic or paramagnetic impurities is observed in all the materials investigated in this study except quartz. In contrast, the magnetic response of quartz is typical of a diamagnet over the temperature range 5 K to 300 K. The volume susceptibility is equal to −4.4×10−7 (cgs) over the whole temperature range.

scholarly journals Theoretical Study of Upper Critical Magnetic Field (HC2) in Multiband Iron Based Superconductors

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Tsadik Kidanemariam ◽  
Gebregziabher Kahsay
Keyword(s):  
Magnetic Field ◽  
Phase Diagrams ◽  
Penetration Depth ◽  
Coherence Length ◽  
Symmetry Axis ◽  
Critical Magnetic Field ◽  
Ginzburg Landau ◽  
Iron Based Superconductors ◽  
Upper Critical Magnetic Field ◽  
Iron Based

This research work focuses on the theoretical investigation of the upper critical magnetic field,HC2; Ginzburg-Landau coherence length,ξGL(T); and Ginzburg-Landau penetration depth,λGL(T), for the two-band iron based superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs. By employing the phenomenological Ginzburg-Landau (GL) equation for the two-band superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs, we obtained expressions for the upper critical magnetic field,HC2; GL coherence length,ξGL; and GL penetration depth,λGL, as a function of temperature and the angular dependency of upper critical magnetic field. By using the experimental values in the obtained expressions, phase diagrams of the upper critical magnetic field parallel,HC2∥c, and perpendicular,HC2⊥c, to the symmetry axis (c-direction) versus temperature are plotted. We also plotted the phase diagrams of the upper critical magnetic field,HC2versus the angleθ. Similarly, the phase diagrams of the GL coherence length,ξGL, and GL penetration depth,λGL, parallel and perpendicular to the symmetry axis versus temperature are drawn for the superconductors mentioned above. Our findings are in agreement with experimental observations.

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