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

Abstract

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.

Magnetoelectric coupling at metal surfaces

“…A Japanese group found large changes in the anisotropy of magnetic thin films in TMR junctions under application of high electric fields [12]. A bistable toggle switching of the magnetization direction between two bistable orientations has been reported very recently by the same group [13]. Against this background, we used a scanning tunneling microscope (STM) to study MEC and were able to demonstrate for the first time bistable switching of the magnetic order on the nanoscale.…”

“…The presence of a constant electric field may influence the magnetic order, but it does not break time reversal symmetry and thus cannot be used to switch between two bistable magnetization directions of a ferromagnet. Two years later, in the same group, Shiota et al [13] showed that in a TMR junction the magnetization can be switched between two orientations by nanosecond voltage pulses. Using asymmetrically shaped voltage pulses, they could break time reversal symmetry and induce a coherent rotation of the magnetization.…”

“…The recent success of a change of magnetization direction in micro-fabricated MTJs which persists at room temperature signifies an important step towards possible applications of MEC [13].…”

Effect of Electric Field on Magnetism of Ni Thin Films via Antiferromagnetic NiO

“…In fact, the voltage-induced magnetization switching was demonstrated for FeCo thin films [1]. The idea to control magnetization by the electric field has been proposed as a multiferroic concept, and has been realized, for instance, in BiFeO 3 , which is one of the most typical multiferroic materials.…”

Ferroelectric Control of Magnetocrystalline Anisotropy at Cobalt/Poly(vinylidene fluoride) Interfaces

“…13 Theoretically, the electric field effect on the MCA was investigated for various free-standing magnetic metal films 10,14-17 and Fe/MgO interfaces. 18,19 Very recently, electrically induced bistable magnetization switching was realized in MgO-based magnetic tunnel junctions at room temperature, 20,21 demonstrating the capabilities of this approach for magnetic data storage applications. 22 Alternatively, the interface magnetic anisotropy (and hence the magnetization orientation) may be tailored electronically by the ferroelectric polarization of an adjacent ferroelectric film.…”