New research paves the way for the development of a high-density MRAM with high-speed and low-power operation.

Among the emerging technologies that have been developed to overcome the scaling problem of current Si-based electronics, magnetic random-access memory (MRAM) consisting of magnetic thin films seems particularly promising as it allows the development of non-volatile memory devices with high operation speed and high density. For that reason, MRAM is being widely investigated by most major microelectronics companies for next-generation memory devices.

MRAM can be applied in so-called “logic-in-memory” devices, in which logic and memory functionalities coexist, thereby drastically improving the performance of semiconductor devices. However, the conventional MRAM technology has a limitation in increasing the operation speed while maintain its high density.

Prof. Byong-Guk Park (Materials Science and Engineering, KAIST) in collaboration with Prof. Kyung-Jin Lee (Materials Science and Engineering, Korea University) have succeeded in developing an MRAM technology that can operate 10 times faster than conventional MRAM without sacrificing chip density.

This technology utilizes the recently-discovered spin-orbit torque (SOT) phenomenon, originating from the interaction between the spin and orbit of electrons. In conventional SOT-based MRAM, ultra-fast data writing can be done by current-induced SOT with the help of an external magnetic field. The latter, however, is detrimental for high-density memory applications. Prof. Park’s research team is tackling this critical challenge by introducing a new material, an antiferromagnet (IrMn). The antiferromagnet generates a sizable SOT effect as well as an exchange-bias field, which enable successful data writing without an external magnetic field. This result paves a new way for the development of an MRAM chip with simple device structure and consequent high-density MRAM.

The application of the non-volatile and high-speed SOT-MRAM in computers or smart phones can allow “normally-off computing,” which does not consume electricity while the devices are not working. Moreover, SOT-MRAMs can be also utilized in diverse low-power electronics such as mobile, wearable, and internet-of-things (IoT) devices.

An article on this research entitled “Field-free switching of perpendicular magnetization through spin-orbit torque in antiferromagnet/ferromagnet/oxide structures” was published on July 11^th, 2016 in Nature Nanotechnology (http://dx.doi.org/10.1038/nnano.2016.109).

Figure 1. Schematic of an SOT-MRAM with an antiferromagnet(IrMn)/ferromagnet(CoFeB) structure. The antiferromagnet IrMn generates SOT as well as an exchange-bias field, which allow data writing without an external magnetic field.

Figure 2. Schematic of the magnetization switching mechanism in an SOT-MRAM device (left). The result shows deterministic switching performance without an external magnetic field (right)