Regensburg 2004 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Tiefe Temperaturen

TT 8: Postersitzung I: Supraleitung

TT 8.2: Poster

Montag, 8. März 2004, 14:30–19:00, Poster A

Preparation, Structure, and Properties of Hg,Re-Containing High-Temperature Superconductor Thin Films — •Abouelwafa Salem, Gerhard Jakob und Hermann Adrian — Institut für Physik, Johannes Gutenberg–Universität, 55099

Fully textured (Hg_0.9Re_0.1)Ba₂CaCu₂O_6+δ (HgRe-1212) thin films have been prepared by pulsed laser deposition (PLD) and post-annealing. The films exhibit sharp superconducting transitions at T_c= 124 K with transition widths of Δ T_c ≃ 2 K. Conditions for reproducible film preparation have been found. The resistive transitions have been investigated in magnetic fields up to 8 T (parallel to the c-axis) and 10 T (perpendicular to the c-axis). The activation energy of thermally activated flux-motion has been determined for both magnetic field orientations. The Hall resistivity (ρ_xy) has been measured in the ab-plane at 8 T. In the mixed state a power-law behavior is observed, where ρ_xy scales to ρ_xx: ρ_xy = A ρ_xx^β, with β = 1.4 ±0.1. Above 130 K the T ² dependence of the cotangent of the Hall angle is observed. Magnetization loops were measured at various temperatures in a SQUID magnetometer. The corresponding critical current densities J_c were calculated. The anisotropic properties of the vortex state and the depinning field B_dp(θ) have been studied by varying the angle θ between the field direction and the c-axis of the film. The measured angular dependence B_dp(θ) shows a cusp for θ = 90^∘. The films exhibit a rather low critical field anisotropy of 7.7. Under the same conditions (Hg_0.9Re_0.1)Ba₂Ca₂Cu₃O_8+δ (HgRe-1223) thin film (T_c= 130 K) have been prepared.