Magnetic properties of YBCO single-crystal grown on Y ₂ O ₃ layer by a cold top-seeding method

In this work, single-crystal samples 20 mm in diameter were grown by a cold top-seeding method. In order to study the effect of an Y ₂ O ₃ buffer layer, a compacted precursor was located in a crucible on a buffer layer of freely poured Y ₂ O ₃ powder. The YBCO bulk samples were carefully prepared in the same chemical composition. In order to examine the homogeneity of the samples, rectangular specimens were cut from a sample. The structural orientation of the specimens was measured by a X-ray diffractrometer (XRD). The microstructure was observed with a Scanning Electron Microscope (SEM). The magnetic properties were measured using a Vibrating Sample Magnetometer (VSM) at 77 K with the applied magnetic field parallel to the c-axis. As a result only (00l) peaks were observed in X-ray diffraction data, indicating that all specimens are highly oriented with the c-axis perpendicular to the top surface. Also the cut samples exhibited very fine Y211 inclusion distributed in the bulk sample observed in SEM micrographs. The critical current density J _c (A/cm ² ) has been estimated by the extended Bean model. The maximum value of the critical current density at 77 K is 5.2×10 ⁴ A/cm ² in a self-field. The trapped magnetic fieldmeasurements of the samples were performed by using Hall probe scanning device with static field of 0.5 T at 77 K. The single-domain sample exhibits a trapped field of 1140 G at 77 K.