AsianScientist (Mar. 28, 2016) – For the past few decades, much effort has been devoted to the development of magnetic random access memories (MRAMs), which store information as the magnetization direction of a magnet. Researchers in Japan have succeeded in developing a new-structure magnetic memory device using spin-orbit torque-induced magnetization switching.
The work, led by Professor Hideo Ohno and Associate Professor Shunsuke Fukami of Tohoku University, was published in Nature Nanotechnology.
Since the magnetization can generally be reversed at an unlimited high speed, the MRAMs are regarded as a promising replacement for semiconductor-based working memories that are currently in use, such as static random access memories and dynamic random access memories. The main challenge of MRAM development, however, is how to achieve magnetization reversal efficiently.
Recently, there has been intensive study into spin-orbit-torque (SOT)-induced magnetization switching, which makes use of torques brought about by an in-plane current through spin-orbit interactions. In principle, the SOT-induced switching allows for an ultrafast magnetization reversal within nanoseconds.
While there are been switching schemes where the magnetization is directed orthogonally to the applied write current, the present structure developed by the Tohoku University researchers has the magnetization directing parallel to the current.
The group fabricated three-terminal devices with the new structure, comprising of a Ta/CoFeB/MgO-based magnetic tunnel junction, and successfully demonstrated the switching operation.
The required current density to induce the magnetization switching was reasonably small and the resistance difference between the “0” and “1” states was reasonably large, indicating that the new structure is a promising candidate for MRAM applications.
In addition, the group showed that their structure has the potential to help researchers delve deeper into the physics of SOT-induced switching, around which a number of questions remain.
The magnetic memory device can store the information without a power supply, allowing a drastic reduction of the power consumption of integrated circuits. In particular, this is a significant benefit for applications that have relatively long standby times, such as sensor nodes which are likely to perform important roles in future IoT (Internet of Things) societies.
In this regard, the present work is expected to pave the way toward the realization of ultra low-power and high-performance integrated circuits.
The article can be found at: Fukami et al. (2016) A Spin-orbit Torque Switching Scheme with Collinear Magnetic Easy Axis and Current Configuration.
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Source: Tohoku University; Photo: Dick Thomas Johnson/Flickr/CC.
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