Anisotropic magnetic relaxation, hysteresis, and Meissner fraction in untwinned single-crystal YBa2Cu3O7−δ produced without applying stress

Abstract

By quenching the tetragonal phase during crystal growth of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ and then oxygenating the crystals without mechanical stress, we obtain some essentially untwinned crystals. Magnetic measurements on such crystals, with fields applied along the a or b axis, show anisotropy. A qualitative analysis of our relaxation and hysteresis data indicates that the critical current density is higher along a than along b (the chain direction). The anisotropic Meissner percent data show that pinning is higher for fields along b than along a.