Angular Hysteresis in the Critical Current Density of Laser-Patterned REBa2Cu3Oy Films

The transport critical current density J_c as a function of applied magnetic field orientation was measured for REBa₂Cu₃O_y (RE:Yb,Y,Dy) films that were line-patterned to make a micro bridge (20 mum x 2 mm) with an etched line-width of 20 mum by laser etching. The angular dependent J_c(thetas) curves measured for increasing thetas were found to be different from those measured for decreasing thetas. The angular hysteresis in J_c(thetas) appeared more prominently at low temperatures and in low magnetic fields, e.g. at 40 K and at 0.1 T. For similar REBa₂Cu₃O_y films that were plane-patterned by UV photolithography into narrow strips, angular hysteresis was not observed. The hysteresis in J_c (thetas) was found to be closely related to the hysteresis in Jc as a function of applied field H, which was also found in line-patterned REBa₂Cu₃O_y films. The origin of the hysteresis in JC(H) of the line-patterned films was examined comparing the experimental results with the results of a theoretical calculation based on a model which assumes that the measured part in the bridge is influenced by the magnetic moment of the electrical terminals part adjacent to it across the etched lines.