  The freeze-in mechanism of dark matter production provides a simple and
intriguing alternative to the WIMP paradigm. In this paper, we analyze whether
freeze-in can be used to account for the dark matter in the so-called singlet
fermionic model. In it, the SM is extended with only two additional fields, a
singlet scalar that mixes with the Higgs boson, and the dark matter particle, a
fermion assumed to be odd under a Z_2 symmetry. After numerically studying the
generation of dark matter, we analyze the dependence of the relic density with
respect to all the free parameters of the model. These results are then used to
obtain the regions of the parameter space that are compatible with the dark
matter constraint. We demonstrate that the observed dark matter abundance can
be explained via freeze-in over a wide range of masses extending down to the
keV range. As a result, warm and cold dark matter can be obtained in this
model. It is also possible to have dark matter masses well above the unitarity
bound for WIMPs.
