Large voltage-induced magnetic anisotropy change in a few atomic layers of iron

• Published in: Nature nanotechnology Vol. 4; no. 3; pp. 158 - 161
• Main Authors: Suzuki, Y, Maruyama, T, Shiota, Y, Nozaki, T, Ohta, K, Toda, N, Mizuguchi, M, Tulapurkar, A. A, Shinjo, T, Shiraishi, M, Mizukami, S, Ando, Y
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.03.2009; Nature Publishing Group
• Subjects: Anisotropy; Electric fields; Electric potential; Electrical junctions; Electrodes; Engineering schools; Ferromagnetic materials; Induced magnetic anisotropy; Iron; letter; Magnesium oxide; Magnetization; Materials research; Materials Science; Memory cells; Memory devices; Nanotechnology; Nanotechnology and Microengineering; Power consumption; Power management; Spintronics; Symmetry; Tunnel junctions; Voltage; Japan
• ISSN: 1748-3387; 1748-3395
• DOI: 10.1038/nnano.2008.406

In the field of spintronics, researchers have manipulated magnetization using spin-polarized currents 1 , 2 , 3 . Another option is to use a voltage-induced symmetry change in a ferromagnetic material to cause changes in magnetization or in magnetic anisotropy 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 . 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 (∼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 3 d 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. A voltage-induced symmetry change in a ferromagnetic material can change its magnetization or magnetic anisotropy, but these effects are too weak to be used in memory devices. Researchers have now shown that a relatively small electric field can cause a large change in the magnetic anisotropy of a few atomic layers of iron. The results could lead to low-power logic devices and non-volatile memory cells.