On the intermediate peak in melt textured YBa2Cu3Oy superconductors

The magnetic hysteresis loops were studied on Pr6O11 added top-seeded melt grown YBa2Cu3Oy (Y123) superconductors. By tailoring the flux pinning sites by praseodymium oxide additions, for the first time, a pronounced intermed iate peak was observed in the magnetisation loops on melt textured Y123 mat erial. The position of the intermediate peak was observed to shift towards lower fields with decreasing temperature in contrast to the fish-tail peak where the field at which the peak appears increases with decreasing tempera ture. The origin of the intermediate peak is assigned as due to the matchin g effect from Pr-substituted regions in the Y123 matrix. The nature and con ditions, which favoured the appearance of the intermediate peak and the rea sons for the shift in its position with temperature, are discussed. A schem atic model, based on the temperature dependent pinning centres, is proposed to explain the peak position with temperature. (C) 2001 Elsevier Science B .V. All rights reserved.