New Memory Device Foreshadows Flexible Electronics

Associate Professor Yang Hyunsoo shows off his team’s flexible memory device. (Image courtesy of NSU).

A team of researchers has recently made a critical breakthrough in the pursuit of flexible electronics. The team successfully developed a high-performance magnetic memory embedded on flexible plastic material, paving the way towards a wide array of applications including wearable electronics, healthcare, and robotics.

What is MRAM?

The new technology uses magnetoresistive random access memory (MRAM), an alternative to more common memory solutions such as dynamic random access memory (DRAM). Unlike DRAM, which stores data via electric charge, MRAM makes use of magnetic storage elements. Although not yet in widespread use, MRAM technology is promising due to its high speed and low power consumption.

The magnetic storage elements of MRAM are formed with two ferromagnetic plates separated by a thin layer of insulation, together called a magnetic tunnel junction (MTJ). By applying an external magnetic field, the direction of the magnetization of the ferromagnetic plates can be controlled.

If the magnetizations are in a parallel orientation, it is likely that electrons will tunnel through the insulating layer. Conversely, if the orientation is antiparallel, there is a much lower rate of tunneling. This allows an MTJ to be in a state of either high or low resistance. Because of this, reading data is as simple as measuring the resistance of the MTJ.

A magnetic tunnel junction (MTJ) consists of two ferromagnetic plates separated by a tunnel barrier only a few nanometers thick. (Image courtesy of Wikipedia).

The novelty of the team’s approach begins with the use of crystalline magnesium oxide (MgO) as the MTJ tunnel barrier. While there has been research in flexible MTJs with tunnel barriers made of alumina, all efforts using MgO-based barriers have exclusively been on rigid substrates. In order to achieve flexibility, the team used a transfer printing process to implant their MgO-based MTJs on a flexible plastic surface made of polyethylene terephthalate. Since MgO barriers offer significantly increased tunneling magnetoresistance over alumina barriers, the development of flexible MgO barrier technology is a huge step forward.

The Future is Flexible

The research team, based at the National University of Singapore (NUS), believes their research marks a significant breakthrough for future flexible technology. Team leader Yang Hyunsoo, an associate professor of the NUS Department of Electrical and Computer Engineering, spoke optimistically about the significance of their results.

"Flexible electronics will become the norm in the near future, and all new electronic components should be compatible with flexible electronics,” he said. “We are the first team to fabricate magnetic memory on a flexible surface, and this significant milestone gives us the impetus to further enhance the performance of flexible memory devices and contribute towards the flexible electronics revolution."

The team published their findings in Advanced Materials under the title Flexible MgO Barrier Magnetic Tunnel Junctions.

For more flexible electronics, read about a stretchable supercapacitor for wearable devices.