  We present a new scenario for the breakdown of ferromagnetic order in a
two-dimensional quantum magnet with competing ferromagnetic and
antiferromagnetic interactions. In this, dynamical effects lead to the
formation of two-magnon bound states, which undergo Bose-Einstein condensation,
giving rise to bond-centered nematic order. This scenario is explored in some
detail for an extended Heisenberg model on a square lattice. In particular, we
present numerical evidence confirming the existence of a state with d-wave
nematic correlations but no long range magnetic order, lying between the
saturated ferromagnetic and collinear antiferromagnetic phases of the
ferromagnetic J1-J2 model. We argue by continuity of spectra that this phase is
also present in a model with 4-spin cyclic exchange.
