  Critical exponents in the CP^{N-1} model, which describes localized-moment
ferro- and antiferromagnets (N=2 in the Heisenberg model), are calculated from
two-particle Green's functions to first order in 1/N. For d=2+\epsilon the
results agree with earlier renormalization group calculations. For d=3 the
leading 1/N-corrections turn out to be very large at N=2. For d=4-\epsilon the
1/N-corrections are small at any N and insufficient to describe correctly the
magnetic phase transition.

Condensed Matter