Induction of coherent magnetization switching in a few atomic layers of FeCo using voltage pulses

The possibility of controlling magnetization by spin-polarized current could lead to devices more energy-efficient than traditional ones using external magnetic fields. Now, an even more efficient method has been demonstrated by using electric-field pulses to switch the magnetization in FeCo magnetic cells. The magnetization direction of a metallic magnet has generally been controlled by a magnetic field or by spin-current injection into nanosized magnetic cells 1 , 2 . Both these methods use an electric current to control the magnetization direction; therefore, they are energy consuming. Magnetization control using an electric field 3 is considered desirable because of its expected ultra-low power consumption and coherent behaviour. Previous experimental approaches towards achieving voltage control of magnetization switching have used single ferromagnetic layers with and without piezoelectric materials, ferromagnetic semiconductors, multiferroic materials, and their hybrid systems 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 . However, the coherent control of magnetization using voltage signals has not thus far been realized. Also, bistable magnetization switching (which is essential in information storage) possesses intrinsic difficulties because an electric field does not break time-reversal symmetry. Here, we demonstrate a coherent precessional magnetization switching using electric field pulses in nanoscale magnetic cells with a few atomic FeCo (001) epitaxial layers adjacent to a MgO barrier. Furthermore, we demonstrate the realization of bistable toggle switching using the coherent precessions. The estimated power consumption for single switching in the ideal equivalent switching circuit can be of the order of 10 4 k B T , suggesting a reduction factor of 1/500 when compared with that of the spin-current-injection switching process.