  The critical behavior of the chiral quark-meson model is studied within the
Functional Renormalization Group (FRG). We derive the flow equation for the
scale dependent thermodynamic potential at finite temperature and density in
the presence of a symmetry-breaking external field. Within this scheme, the
critical scaling behavior of the order parameter, its transverse and
longitudinal susceptibilities as well as the correlation lengths near the
chiral phase transition are computed. We focus on the scaling properties of
these observables at non-vanishing external field when approaching the critical
point from the symmetric as well as from the broken phase. We confront our
numerical results with the Widom-Griffiths form of the magnetic equation of
state, obtained by a systematic epsilon-expansion of the scaling function. Our
results for the critical exponents are consistent with those recently computed
within Lattice Monte-Carlo studies of the O(4) spin system.
