  We investigate non-linear extensions of the holographic soft wall model
proposed by Karch, Katz, Son and Stephanov [1] including non-minimal couplings
in the five-dimensional action. The non-minimal couplings bring a new parameter
$a_0$ which controls the transition between spontaneous and explicit symmetry
breaking near the limit of massless quarks (the chiral limit). In the physical
region (positive quark mass), we show that above a critical value of the
parameter $a_0$ the chiral condensate $\langle \bar{q} q \rangle$ is finite in
the chiral limit, signifying spontaneous chiral symmetry breaking. This result
is supported by the lightest states arising in the spectrum of the pseudoscalar
mesons, which become massless in the chiral limit and are therefore intrepreted
as Nambu-Goldstone bosons. Moreover, the decay constants of the pseudoscalar
mesons also support this conclusion, as well as the Gell-Mann-Oakes-Renner
(GOR) relation satisfied by the lightest states. We also calculate the spectrum
of scalar, vector, and axial-vector mesons with their corresponding decay
constants. We describe the evolution of masses and decay constants with the
increasing of the quark mass and for the physical mass we compare our results
against available experimental data. Finally, we do not find instabilities in
our model for the physical region (positive quark mass).
