RELATIONSHIP BETWEEN THE NEW SUPERCONDUCTORS AND 2-DIMENSIONAL OR 3-DIMENSIONAL ANTIFERROMAGNETISM

With the classical superconductors there is nearly always an opposition with the local or itinerant magnetism. For the new superconductors there is a coexistence regime with the two-dimensional Cu antiferromagnetism of short coherence length, a fact which can be related to a new attractive interaction due to magnetic fluctuations. However, the opposition between this new superconducting state and the three-dimensional antiferromagnetism is analyzed as a function of x proportional to the density of conduction electrons or holes, through the Ginzburg-Landau opposition term gamma-M2-psi(2) between the two order parameters: if gamma is beyond a critical value then there can be no overlap of the two transition temperatures T(CM)(x) and T(CS(x), with nevertheless a common border observed for Nd2-xCexCuO4.