The crossover from two- to three-dimensional critical behavior of nearly antiferromagnetic itinerant electrons is studied in a regime where the interplane single-particle motion of electrons is quantum mechanically incoherent because of thermal fluctuations. This is a relevant regime 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. However, contrary to the usual approaches, cutoffs appear naturally in the microscopic TPSC theory so that parameter-free calculations can be done for Hubbard models with. arbitrary band structure. A general discussion of universality in the renormalized-classical crossover from d=2 to d=3 is also given.

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