Miscibility-gap boundaries in La2CuO4+δ

Determine definitively the lower and upper boundaries of the first miscibility gap in the excess-oxygen concentration δ of La2CuO4+δ and establish how those boundaries depend on sample-preparation methods.

Background

The interpretation of resistive anomalies in oxygen-doped La2CuO4+δ has historically involved phase separation into oxygen- or hole-rich and oxygen- or hole-poor regions. The paper notes that the relevant miscibility gap is central to deciding whether the observed anomalies reflect phase separation or intrinsic bulk properties of the antiferromagnetic–superconducting Cu-O plane.

Existing studies have not fixed the boundaries consistently, and the reported values may vary with crystal growth and oxygen-annealing procedures. The authors therefore identify the determination of these boundaries as an unresolved materials-physics issue.