Abstract
The magnetization curves of crystals are widely observed to exhibit a pronounced low-field minimum in the temperature range 30 K<T<. We demonstrate that these magnetization anomalies correlate with the c-axis lattice parameter, and hence with the specific oxygen deficiency δ. We interpret this low-field feature in terms of a field-induced decoupling of regions of oxygen-rich material by boundaries of oxygen-poor material, a phenomenon reminiscent of the behavior in granular superconductors. A ‘‘phase diagram’’ that demarcates the multigrain onset as a function of temperature and δ is then constructed. The shape of the ‘‘phase boundaries’’ is described using a percolation model. This analysis demonstrates that magnetization is a very sensitive measure of crystal quality.
- Received 29 August 1991
DOI:https://doi.org/10.1103/PhysRevB.45.4916
©1992 American Physical Society