Measurements of critical currents as a function of temperature in YBa₂Cu₃O_7-xthin films: a comparative study

Abstract

The critical current density (Jc) for zero magnetic field has been measured as a function of temperature in c-oriented thin layers of YBa2Cus07, prepared by different synthesis methods. One direct and two indirect J,(n methods were employed for each film: transport measurements on patterned film constrictions, DC remanent magnetization studies using the Bean model and non-linear AC screening analysis. Results from the indirect methods were calibrated against transport data. Possible origins of observed dependences are suggested and calibration procedures are discussed. The investigation demonstrated t h e feasibility of using AC screening analysis in rapid determinations of J,(n close to Tc.

Determination of the critical temperature and oxygen content variations along the c-axis of YBCO epitaxial films

“…for all the films. Maximum critical current densities in this range were also reported by other authors [14,15], although larger j S were measured on films deposited either on vicinal substrates [14] or on nanobridges [16,17] In order to confirm the validity of our determination of the T c profiles, the oxygen content of film B, whose characteristics are reported in Table 1, was measured by Non Rutherford Elastic Resonance Scattering (NRERS) by J.Siejka (INSP-Paris) [19]. The oxygen content of film B was found to be depth dependent.…”

YBa 2 Cu 3 O 7 − δ films with high critical current density on epitaxial films of Ba 2 LaNbO 6 , a new perovskite substrate for YBa 2 CuO 7 − δ supercondu

“…The transport measurements performed with 1600 Å thick and 10 mm wide micro bridge gave J C of 5 × 10 6 A/cm 2 at 77 K under zero magnetic field. The best transport current density values reported recently for a YBCO film deposited on (100) MgO was ∼ 2 × 10 6 A/cm 2 at 77 K in zero magnetic field [14], [15]. The higher current density obtained in our present studies can be due to the chemical non-reactivity of YBCO with BLNO at high processing temperature [12] and the high quality of the YBCO film grown on BLNO.…”

Screening technique measurement of ac imaginary susceptibility and critical current density of YBa2Cu3O7−δ films

“…The integration of ␣ m and ␤ m was done numerically. The Fourier transform of the pick-up signal consists of the first, third, and others odd harmonics, but we only worked with the first and third harmonics because the others are in general negligible, [1][2][3]8 as can be seen in Fig. 2͑c͒.…”

“…[1][2][3][4][5][6][7][8][9][10] With this technique it is possible to study Josephson tunneling 11 and vortex states, 12 determine the critical current density (J c ), 3,4,7 etc. In this technique, the pick-up and compensation coils are connected in series and placed coaxially inside a solenoid that generates a homogeneous ac field in its interior.…”

“…A lock-in amplifier is commonly used to detect the harmonic signal related to the signal distortion when the field penetrates the superconducting sample. 4,8 An ac imaginary susceptibility (Љ) of a ͑Bi, Pb͒ 2 Sr 2 Ca 2 Cu 3 O y /Ag tape was estimated using the screening technique by Xing et al in Ref. 13, with the applied field perpendicular to the tape plane.…”