  Based on recent experimental results for electron-doped cuprate oxides and
ferromagnetic superconductors, it is shown that antiferromagnetic fluctuations
always develop in the superconducting phase of both low- and high-temperature
superconductors. The relation between the magnitude of the antiferromagnetic
pseudogap and the characteristic temperature of the antiferromagnetic pseudogap
opening is obtained. The characteristic temperature of the antiferromagnetic
pseudogap opening for metal superconductors is estimated.
