Magnetism in the insulating parents of the high-Tc superconductors: well or ill understood?

An overview of previous theoretical research on magnetism in the insulating parents of high critical temperature superconductors was presented. The differences between results for covalent reduction of the ordered moment in antiferromagnetic CuO2 planes was analyzed. It was proposed that the covalency reduction in the ordered moment was very large, given the approximate validity of the 3-band model with standard parameter values.