  We show that spin-S chains with SU(2)-symmetric, ferromagnetic
nearest-neighbor and frustrating antiferromagnetic next-nearest-neighbor
exchange interactions exhibit metamagnetic behavior under the influence of an
external magnetic field for small S, in the form of a first-order transition to
the fully polarized state. The corresponding magnetization jump increases
gradually starting from an S-dependent critical value of exchange couplings and
takes a maximum in the vicinity of a ferromagnetic Lifshitz point. The
metamagnetism results from resonances in the dilute magnon gas caused by an
interplay between quantum fluctuations and frustration.
