Crystal growth and characterization of the 4-leg spin ladder compound La₂Cu₂O₅

Crystallization of La₂Cu₂O₅ has been investigated in the La₂O₃-CUO system for various starting compositions both in air and oxygen atmospheres. In air, we find that there exists a new region of crystallization of La₈Cu₇O₁₉ phase, just above that of La₂Cu₂O₅. However, this region vanishes completely in flowing-oxygen atmosphere. By utilizing this, large single crystals of the 4-leg spin-ladder compound La₂Cu₂O₅ have been successfully grown from CuO flux by the slow cooling method. Room-temperature resistivity parallel to the ladder direction (∥b) of the as-grown crystals is estimated to be 1.7×10³ Ω cm. A significant decrease in the resistivity (798 mΩ cm at 300 K) is observed upon hole doping by means of high oxygen pressure annealing (approximately 400 atm) using a hot isostatic pressing furnace. However, no transition was observed from the semiconducting behavior.