  Based on micromagnetic simulations, we report on a novel helical magnetic
structure in a soft magnetic film that is sandwiched between and
exchange-coupled to two hard magnetic layers. Confined between antiparallel
hard magnetic moments, a helix with a turn of 180$^{\circ}$ is stable without
the presence of an external magnetic field. The magnetic stability is
determined by the energy minimization and is a result of an internal field
created by exchange interaction and anisotropy. Since the internal field stores
magnetic energy, the helix can serve as an energy-storing element in spin-based
nanodevices. Due to the significantly different magnetic resonance frequencies,
the ferromagnetic and helical ground states are easy to distinguish in a
broadband ferromagnetic resonance experiment.
