In the field of spintronics, researchers have manipulated magnetization using spin-polarized currents. Another option is to use a voltage-induced symmetry change in a ferromagnetic material to cause changes in magnetization or in magnetic anisotropy. However, a significant improvement in efficiency is needed before this approach can be used in memory devices with ultralow power consumption. Here, we show that a relatively small electric field (less than 100 mV nm(-1)) can cause a large change (approximately 40%) in the magnetic anisotropy of a bcc Fe(001)/MgO(001) junction. The effect is tentatively attributed to the change in the relative occupation of 3d orbitals of Fe atoms adjacent to the MgO barrier. Simulations confirm that voltage-controlled magnetization switching in magnetic tunnel junctions is possible using the anisotropy change demonstrated here, which could be of use in the development of low-power logic devices and non-volatile memory 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. Both these methods use an electric current to control the magnetization direction; therefore, they are energy consuming. Magnetization control using an electric field 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. 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.

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