N-VECTOR SPIN MODELS ON THE SIMPLE-CUBIC AND THE BODY-CENTERED-CUBIC LATTICES - A STUDY OF THE CRITICAL-BEHAVIOR OF THE SUSCEPTIBILITY AND OF THE CORRELATION LENGTH BY HIGH-TEMPERATURE SERIES EXTENDED TO ORDERBETA(21)

High-temperature expansions for the free energy, the susceptibility, a nd the second correlation moment of the classical N-vector model [also known as the O(N) symmetric classical spin-Heisenberg model or as the lattice O(N) nonlinear sigma model] on the simple-cubic and the body- centered-cubic lattices are extended to order beta(21) for arbitrary N . The series for the second field derivative of the susceptibility is extended to order beta(17). We report here on the analysis of the comp uted series for the susceptibility and the (second moment) correlation length which yields updated estimates of the critical parameters for various values of the spin dimensionality N, including N = 0 (the self -avoiding walk model), N = 1 (the Ising spin-1/2 model), N = 2 (the XY model), and N = 3 (the classical Heisenberg model). For all values of N we confirm a good agreement with the present renormalization-group estimates. A study of the series for the other observables will appear in a forthcoming paper.