Oscillators and methods of manufacturing and operating the same are provided, the oscillators include a pinned layer, a free layer and a barrier layer having at least one filament between the pinned layer and the free layer. The pinned layer may have a fixed magnetization direction. The free layer corresponding to the pinned layer. The at least one filament in the barrier layer may be formed by applying a voltage between the pinned layer and the free layer. The oscillators may be operated by inducing precession of a magnetic moment of at least one region of the free layer that corresponds to the at least one filament, and detecting a resistance change of the oscillator due to the precession.