  The ability to control the magnetization switching in nanoscale devices is a
crucial step for the development of fast and reliable techniques to store and
process information. Here we show that the switching dynamics can be controlled
efficiently using a microwave field with slowly varying frequency
(autoresonance). This technique allowed us to reduce the applied field by more
than $30%$ compared to competing approaches, with no need to fine-tune the
field parameters. For a linear chain of nanoparticles the effect is even more
dramatic, as the dipolar interactions tend to cancel out the effect of the
temperature. Simultaneous switching of all the magnetic moments can thus be
efficiently triggered on a nanosecond timescale.
