Ahmed Tirbiyine

The pinning properties and the 80 K transformation in κ-(BEDT-TTF)2Cu[N(CN)2]Br organic superconductor

We have investigated the magnetic measurements on organic superconductor k-(BEDT-TTF)2Cu[N(CN)2]Br. We report hysteresis loops and the associated critical current on both hydrogenated (H8-Br) and deuterated (D8-Br) samples. By cooling the sample at different rates, our results show that the cooling through the order-disorder transformation near 80 K has a dramatic effect on the critical current density and the superconducting transition temperature. The effect is more pronounced in the case of deuterated K-(BEDT-TTF)2Cu[N(CN)2]Br.

MAGNETIZATION MEASUREMENTS IN THE 80 K TRANSFORMATION FOR DEUTERATED ORGANIC SUPERCONDUCTOR κ-(BEDT-TTF)2Cu[N(CN)2]Br

In this paper, we report systematic magnetic measurements on deuterated organic superconductor (κ-D8-Br)κ-(BEDT-TTF)2Cu[N(CN)2]Br. The irreversibility line Hirr(T) and the critical current density Jc were studied. Our results show the strong dependence of Hirr(T) and Jc 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. The irreversible magnetization becomes null at Hirr and vortices are not pinned; therefore they can displace more freely for an increase of the field or the temperature.

Study of the critical current density and the thermodynamic critical field in deuterated κ-(BEDT-TTF)2Cu[N(CN)2]Br organic superconductor

ABSTRACT We have studied the reversible and irreversible part of the hysteresis loops as a function of slow cooling rate through the order–disorder transformation near 80 K for the deuterated (κ-D8-Br) κ-(BEDT-TTF)2Cu[N(CN)2]Br organic superconductor. We estimated the critical current density JC and the thermodynamic critical field HC from the magnetic hysteresis loops. Temperature dependence of the critical current density derived from the irreversible part using Bean’s model. The thermodynamic critical field HC has been obtained from the reversible part of the hysteresis loops.

Noise Spectral Density and Vortex Velocity in YBCO Thin Film at High Critical Temperature

We have studied the voltage noise Vnoise and the voltage noise spectral density Sv of YBaCuO superconductor in the regime of high magnetic field. Our measurements were taken for different temperatures covering the vortex-glass and vortexliquid transition which represents the Tg temperature glass, The voltage noise spectral density Sv(f, T, H) as a function of frequency exhibits 1/f behaviour according to a lorentzian shape A((1+ πf/f0) ), where the constants A, f0, B and C are all determined, and temperature has a strong influence. in addition, we study the variation in the velocity of the vortex as a function of temperature.