Stabilization of helical magnetic structures in thin multilayers

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.