A joint research group that included scientists from Osaka University, Tokyo Institute of Technology and University of York has achieved what is reportedly the world's highest level performance index (magnetic electrical coupling coefficient) in developing a high-performance interfacial multiferroic structure for new voltage information writing technology in spintronics devices. At the same time, they successfully demonstrated repeated switching of nonvolatile memory states by applying an electric field.
A challenge for magnetoresistive memory (MRAM), which is expected to become the next-generation of nonvolatile memory devices, is that it consumes a large amount of power because current is passed through its metallic magnetic material when information is written. The research group has demonstrated a high-performance interfacial multiferroic structure consisting of a high-performance metallic magnetic material and a piezoelectric material bonded together using their own technology, and developed a technology to switch the magnetization direction of the metallic magnetic material efficiently by simply applying voltage instead of an electric current.
The team fabricated a new interfacial multiferroic structure combining Co2FeSi, a kind of Co-based Heusler alloy magnet known for its high spin polarization ratio as a ferromagnet, and Pb(Mg1／3 Nb2／3 )O3 -PbTiO3 (PMNPT), a type of piezoelectric material with high piezoelectric performance, with high quality, and succeeded for the first time in the world in achieving a magnetic-electric coupling coefficient of 1.0x10-5 s/m, which was a barrier to practical use. Furthermore, they realized repeated switching of nonvolatile memory states by applying an electric field.
"This is a low-power information writing technology that can be incorporated into all next-generation spintronics devices, including MRAM," says Osaka University's Professor Hamaya. "Going forward, we would like to advance our research with a view to integrating it with next-generation semiconductor devices and develop it into a technology to overcome the problem of power consumption, which has seen an explosive increase as an issue amid the development of IoT and AI technologies."