The role of excess Cu on La2CuO4 system

The Cu-rich La2CuO4+delta ([La]:[Cu] = 2:1 + x) samples with 0 less than or equal to x less than or equal to 0.18 are characterized using X-ray diffra ction, transmission electron microscopy and electron energy loss spectrum m ethods. The excess Cu is identified to occupy the La site and the maximum o f such substitution, i.e., the maximum of excess Cu content, x, is examined to be about 0.06. From the magnetization measurements of the samples with different excess Cu, we find that the substitution of Cu for La can remarka bly enhance the three-dimensional antiferromagnetic exchange interaction, t hus, promoting electronic phase separation in La2CuO4+delta system with del ta < 0.01. (C) 2001 Elsevier Science B.V. All rights reserved.