Phase diagram of an anisotropic frustrated ferromagnetic spin-1/2 chain in a magnetic field: A density matrix renormalization group study

We study the phase diagram of a frustrated spin-1/2 ferromagnetic chain with anisotropic exchange interactions in an external magnetic field using the density matrix renormalization group method. We show that an easy-axis anisotropy enhances the tendency toward multimagnon bound states while an easy-plane anisotropy favors chirally ordered phases. In particular, a moderate easy-plane anisotropy gives rise to a quantum phase transition at intermediate magnetization. We argue that this transition is related to the finite-field phase transition experimentally observed in the spin-1/2 compound LiCuVO4.