IMPROVEMENT OF THE SUPERCONDUCTING TRANSITION AND DEMAGNETIZATION FACTOR IN YBA2CU3O7-DELTA SINGLE-CRYSTALS BY LASER CUTTING

Single crystals of YBa2Cu3O7-delta have been cut into disc shapes usin g an excimer laser. The bulk superconducting transition was found to b e sharpened in all cases measured. This is associated with the removal of material at the edges which may be depleted of oxygen or otherwise damaged. The magneto-optical images for one crystal have been correla ted with the optical image. The angular dependence of the demagnetizin g factor for field applied in the plane was drastically reduced in dis c-shaped crystals relative to rectangular ones. The held of first flux entry was also increased. (C) 1996 American Institute of Physics.