Magnetism in the insulating parents of the high-T c superconductors: Well or ill understood?

Abstract
We discuss appreciable differences between the results for the covalent reduction of the ordered moment in antiferromagnetic CuO2 planes obtained by various groups, including the present authors. We explain the differences as due to differences in definition, the definition that we used being closely based on experiment (magnetic neutron Bragg scattering), in contrast to the others. We also discuss the large difference between the zero‐point spin fluctuations as calculated by one of the groups and the well‐known result of spin wave theory.