Ultrafast generation of magnetic fields in a Schottky diode

For the development of future magnetic data storage technologies, the ultrafast generation of local magnetic fields is essential. Subnanosecond excitation of the magnetic state has so far been achieved by launching current pulses into micro-coils and micro-striplines1,2,3,4,5,6 and by using high-energy electron beams7. Local injection of a spin-polarized current through an all-metal junction has been proposed as an efficient method of switching magnetic elements8,9, and experiments seem to confirm this10,11,12,13. Spin injection has also been observed in hybrid ferromagnetic–semiconductor structures14,15. Here we introduce a different scheme for the ultrafast generation of local magnetic fields in such a hybrid structure. The basis of our approach is to optically pump a Schottky diode with a focused, ∼150-fs laser pulse. The laser pulse generates a current across the semiconductor–metal junction, which in turn gives rise to an in-plane magnetic field. This scheme combines the localization of current injection techniques11,12,13,16 with the speed of current generation at a Schottky barrier. Specific advantages include the ability to rapidly create local fields along any in-plane direction anywhere on the sample, the ability to scan the field over many magnetic elements and the ability to tune the magnitude of the field with the diode bias voltage.