International Journal of Computer Applications (0975 – 8887) Volume 81 – No.7, November 2013 9 Noise Spectral Density and Vortex Velocity in YBCO Thin Film at High Critical Temperature Abdelhalim HAFID Laboratory of Superconductors Materials at High Critical Temperature University Ibn Zohr Agadir, Morocco Hassan Elouaddi Laboratory of Superconductors Materials at High Critical Temperature University Ibn Zohr Agadir ,Morocco Brahim LMOUDEN Laboratory of Superconductors Materials at High Critical Temperatue University Ibn Zohr Agadir, Morocco Ahmed TAOUFIK Laboratory of Superconductors Materials at High Critical Temperature University Ibn Zohr Agadir, Morocco Mustapha BGHOUR Laboratory of Superconductors Materials at High Critical Temperature University Ibn Zohr Agadir, Morocco Ahmed Tirbiyine Equipe MSISM Universit´e Cadi Ayyad, Facult´e Poly-Disciplinaire, B. P. 4162 Safi, Morocco Abella BOUAADDI Laboratory of Superconductors Materials at High Critical Temperature University Ibn Zohr Agadir, Morocco Habiba El Hamidi Laboratory of Superconductors Materials at High Critical Temperature University Ibn Zohr Agadir, Morocco Abdelhakim NAFIDI Laboratory of Condensed Matter Physics and Nanomaterials for Renewable Energy, - Ibn Zohr University, morocco. ABSTRACT We have studied the voltage noise V noise and the voltage noise spectral density S v of YBaCuO superconductor in the regime of high magnetic field. Our measurements were taken for different temperatures covering the vortex-glass and vortex- liquid transition which represents the T g temperature glass, The voltage noise spectral density S v (f, T, H) as a function of frequency exhibits 1/f behaviour according to a lorentzian shape A((1+ πf/f 0 ) B ) C , where the constants A, f 0 , 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. Keywords Superconductors, vortex velocity, YBCO, power spectral density, dynamic of vortex. 1. INTRODUCTION The scientists have paid a lot of attention to the dynamic of the vortices in order to comprehend to mixed state of HTC superconductors. Since the discovery of those materials in 1986, their investigation becomes the centre of interest of several works. The experimental [1, 2, 3] theoretical [4, 5] investigations show that the vortex matter exhibits diverse properties and a various phase transitions in the mixed state It is obvious that whenever a HTc superconductor carries a transport current, the vortices are induced to move along the sample. Thus, a flux flow dissipation mechanism is generated in the superconductor. the study of noise in high temperature critical superconductor is an adequate way to search for disorder and dynamics of vortices in such materials [6], also to understand the origins of excess conducting noise [7, 8] . Van gurp and Von Ooijen were the first researchers to use this technique for this purpose [9]. In this work, we are interested with the measurements of the voltage noise spectral density S v of YBaCuO. The main findings of this search are: 1. The voltage noise spectral density S v (f) is inversely proportional to the frequency (1/f) according to Lorentzian shape A((1+ πf/f 0 ) B ) C . A, f 0 , B and C are determined by fitting for a magnetic field H= 14T and several temperatures covering different states. 2. Temperature glass T g , represents a point of transition between a high and a weak noise spectral, depending on the motion of vortex [10], and variation of vortex velocity as function as temperature. 2. EXPERIMENTAL PROCEDURE The studied sample was a high quality single crystal YBa 2 Cu 3 O 7-δ thin film deposited by the laser ablation method on the surface (100) of a SrTiO 3 substrate. In zero magnetic field, the resistance vanished at T c = 90 K. The c-axis was perpendicular to the surface of the film. Electrodes of measurements were in gold and deposited on the surface of the sample by in situ evaporation. The film thickness and width were 400 nm and 7.53 μm, respectively. The distance between electrodes of measurements was 135 μm. Contact resistances were less than R=1 [11].