CA4CU5O10 - COPPER-OXIDE CHAINS HIGHLY OCCUPIED BY ZHANG-RICE SINGLETS

The crystal structure of Ca2+xY2-xCu5O10 consists solely of one-dimens ional copper-oxygen chains made from CuO4 squares sharing edges. Over the range of x between 0 and 2, here synthesized using high-pressure o xygen annealing, formal copper valences between 2 and 2.4 can be obtai ned. All the members of the series are electrically insulating, Magnet ization measurements show long-range antiferromagnetic ordering near x =0, with decreasing T-N on increasing x, and the appearance of a new k ind of short-range-ordered state for x greater than 1.5. The high hole concentration regime represents the first observation of the magnetic and transport properties of a mixture of Zhang-Rice singlets and magn etic copper on one-dimensional chains without the complication of addi tional copper-oxygen units, and may be an excellent model system for s tudying their spin and charge dynamics as a key to understanding the b ehavior of CuO2 planes in copper oxide superconductors. [S0163-1829(98 )00329-4].