CROSSOVER FROM 2-DIMENSIONAL TO 3-DIMENSIONAL CRITICAL-BEHAVIOR FOR NEARLY ANTIFERROMAGNETIC ITINERANT ELECTRONS

The crossover from two- to three-dimensional critical behavior of near ly antiferromagnetic itinerant electrons is studied in a regime where the interplane single-particle motion of electrons is quantum mechanic ally incoherent because of thermal fluctuations. This is a relevant re gime for very anisotropic materials like the cuprates. The problem is studied within the two-particle self-consistent (TPSC) approach, which has been previously shown to give a quantitative description of Monte Carlo data for the Hubbard model. It is shown that the TPSC approach belongs to the n-->infinity limit of the O(n) universality class. Howe ver, contrary to the usual approaches, cutoffs appear naturally in the microscopic TPSC theory so that parameter-free calculations can be do ne for Hubbard models with. arbitrary band structure. A general discus sion of universality in the renormalized-classical crossover from d=2 to d=3 is also given.