| MRAM, using magnetism due to electron spin
| When the magnetization directions of two magnetic materials are the same or opposite, 0 or 1 is recorded.
| Magnetization direction also found to be due to asymmetric interaction

With the development of the IT industry, the demand for new storage devices capable of processing and storing large amounts of information is continuously increasing. Accordingly, research on the development of new memory devices that can achieve fast operation speeds and high integration is attracting attention.

Professor Jeong Myeong-hwa's research team at Sogang University has proven the possibility of further improving the speed and storage capacity of magnetic random access memory (MRAM), a next-generation memory semiconductor, by elucidating the magnetic interactions hidden between magnetic materials.

The results of this study were published on the 3rd in the international materials journal ‘Nature Materials’ under the title ‘Long-range chiral exchange interaction in synthetic antiferromagnets’.

In the current information age where real-time video playback anywhere and IoT are becoming a familiar thing, the development of large-capacity information storage devices is active. Among them, MRAM is attracting attention for its non-volatility that does not lose stored information even when power is cut off, and its high-speed operation, and has recently been commercialized.

Unlike conventional memory based on electric current, MRAM uses magnetism generated by the spin of electrons.

When the magnetization directions of two magnetic materials are the same or opposite, information of 0 or 1 is recorded. Despite its many advantages, it has the limitation of requiring a large amount of power to change its magnetization direction.
(a) Schematic diagram of asymmetric interactions in single-layer and multilayer units of magnetic thin films. (b) Schematic diagram of spin states that change with a horizontal magnetic field when the spin directions of two magnetic layers are parallel and antiparallel to each other. (c) Schematic diagram of the experimental method.

The research team discovered that in magnetic materials, there are two magnetization directions (same/opposite directions) due to symmetric interactions, as well as magnetization directions due to asymmetric interactions. By storing information in a three-dimensional spin structure, the speed and capacity of MRAM can be greatly improved.

The asymmetric interaction revealed in this study occurs when the symmetry is broken by a non-magnetic material between two magnetic materials. It is reproduced regardless of the type of magnetic material. It has academic significance in that it elucidates a new magnetic interaction hidden between two magnetic materials.
(a) Magnetization curves measured when applying a horizontal magnetic field to a single layer and multilayer (spin directions parallel and antiparallel) of a magnetic thin film. (b, c) Symmetric and asymmetric switching results measured by varying the horizontal magnetic field angle.

By exploiting asymmetric magnetic interactions, it is possible to construct not only symmetric spin structures with the same/opposite directions, but also asymmetric unusual spin structures in magnetic materials. This makes it possible to apply new concept non-volatile memory devices that go beyond the binary system of 0 and 1 and are fast and have large data capacity.

Professor Jeong Myeong-hwa said, “This study is significant in that it has revealed a new, previously unknown magnetic interaction between magnetic thin films,” and added, “It is expected to contribute to overcoming the storage capacity limitations of future memory devices and solving the structural problems of magnetic materials, thereby designing new types of MRAM devices.”