We present exact analytic results for the energy of a SU(N) repulsive
Fermi gas as a function of the spin-channel occupation at second order
in the gas parameter. This is an extension of previous results that now
incorporates the degree of polarization of the system. Therefore, the
magnetic properties of the gas can be obtained, free from numerical
uncertainties. For spin 1/2 we find that second-order corrections change
the itinerant ferromagnetic transition from continuous to first-order.
Instead, for spin larger than 1/2 the phase transition is always of
first-order type. The transition critical density reduces when the spin
increases, making the phase transition more accessible to experiments
with ultracold dilute Fermi gases. Estimations for Fermi gases of Yb and
Sr with spin 5/2 and 9/2, respectively, are reported.