A research group led by Professor Yasuo Ando at Graduate School of Engineering, Tohoku University (Professor and the Dean Masaru Uchiyama) has succeeded in developing a Magnetic Tunnel Junction (MTJ; a nanostructured device using magnet) with a world record performance. MTJ is one of elements of a nonvolatile integrated circuit, combining a nonvolatile memory function with a computing function. Nonvolatile integrated circuits are expected to be an environment-responsive electronic device with as lower power consumption as possible. The research results are a breakthrough to develop the nonvolatile integrated circuit, and a great step toward practical use of them.

The basic structure of MTJ used as a signal reading element for a high performance hard disc drive is that an extremely thin insulating film with several atoms is between two thin ferromagnetic films. However, improvements of signal output in the structure have come close to the limit both experimentally and theoretically. The research group has succeeded in increasing signal output by 70% with double-layered tunnel barrier in MTJ structure using three ferromagnetic films and two insulating films.

Increasing the performance of the memory elements helps significantly reduce power consumption while nonvolatile integrated circuits are operating. This element may also be applicable as a spin-transistor, which is using the large signal changes as a switching operation. Integrated circuits and transistors by semiconductors are widely used through the industry to households, especially to personal cellular phones. However, power saving of the semiconductor devices is becoming a big problem. Mounting nonvolatile devises on all the electric devises is expected to help significantly reduce power consumption and CO2 emission.

This research was supported by the Research and Development for Next-Generation Information Technology by Ministry of Education, Culture, Sports, Science and Technology (led by Professor Hideo Ohno, Research Institute of Electrical Communication, Tohoku University). Some experiments in an early stage on the research have been performed by Japan-China Joint Research at Japan Society for the Promotion of Science (JSPS.) ULVAC, Inc. has helped to make elements. The research results have been published in Applied Physics Express (APEX, an online journal) on July 17, 2009.

[Contact]
Professor Yasuo Ando
Graduate School of Engineering, Tohoku University
Tel: +81 22-795-7946
e-mail: ando@mlab.apph.tohoku.ac.jp

Assistant Professor Hiroshi Naganuma
Tel: +81 22-795-7949
e-mail: naganuma@mlab.apph.tohoku.ac.jp