  The frustrated ferromagnetic spin-1/2 Heisenberg chain is studied by means of
a low-energy field theory as well as the density-matrix renormalization group
and exact diagonalization methods. Firstly, we study the ground-state phase
diagram in a magnetic field and find an `even-odd' (EO) phase characterized by
bound pairs of magnons in the region of two weakly coupled antiferromagnetic
chains. A jump in the magnetization curves signals a first-order transition at
the boundary of the EO phase, but otherwise the curves are smooth. Secondly, we
discuss thermodynamic properties at zero field, where we confirm a double-peak
structure in the specific heat for moderate frustrating next-nearest neighbor
interactions.
