Spontaneous magnetization and antiferromagnetic correlations of the CuO₂ chains in Sr_0.73CuO₂

We have studied magnetic properties of the novel quasi-one-dimensional cuprate Sr0.73CuO2, containing edge-sharing CuO2 chains. This compound can be described as an alternating-chain Heisenberg antiferromagnet. The CuO 2 chains are hole doped with a high hole concentration (∼0.6/CuO2), and each hole renders the CuO 2 unit nonmagnetic. The experiments reveal that Sr0.73CuO2 develops a long-range magnetic order at 12 K with a small spontaneous ferromagnetic moment Ms= 3.2(2)×10-3μB/Cu. The observation of long-range magnetic order in CuO 2 chains doped with a substantial number of holes is very surprising. © 1998 The American Physical Society.