KONDO CROSSOVER IN THE SELF-CONSISTENT ONE-LOOP APPROXIMATION

The free energy and magnetization for the general SU(N) one-impurity Kondo model in the magnetic field h are calculated by extending the previous 1/N expansion technique: the saddle point is determined self-consistently to the 1/N order. The obtained universal field-dependent magnetization M(h/T(K)) by this simple method is shown analytically to be asymptotically exact at both h much less than T(K) and h much greater than T(K) limits. For general ''f-electron'' fillings, except half filling, the M(h/T(K)) curves cross continuously from the weak to strong coupling limit, but overestimate the curvature in the crossover region for moderate N. The magnetic Wilson crossover numbers are calculated approximately. Our results explicitly verify that the 1/N parameter is nonsingular under the adiabatic continuation.