There are many phenomena induced by light irradiation in daily lives and in modern advanced science and technology. Plant photosynthesis and photocatalyst used for the walls of a hospital are part of examples. It is known that when a matter was irradiated with pulsed laser, its state will instantly and dramatically change. This phenomenon is called photo-induced phase transition and has industrially gathered attention for an alternative device material to realize high-speed switch.

 A research group led by Associate Professor Sumio Ishihara at Graduate School of Science, Tohoku University has focused attention on magnetization induced by light irradiation and successfully reproduced the process by a large-scale simulation using a parallel computer. The research result explains a mechanism of the magnetization at the microscopic level. Domestic and overseas experimental studies have shown that pulsed laser irradiation to insulating metal oxides induces magnetic metallic property. In this simulation, the process of changing into metallic magnet from insulator was observed in two stages. Metallization and magnetization occur cooperatively in an extremely unstable state in the first stage just after light irradiation. The first stage lasts only for 10 picoseconds, and only magnetization develops in the second stage. The research results are expected to provide a guideline for the new development of nano technology that connects spintronics related magnetic property and conductivity with optical technology.

 
 The research has been conducted in collaboration with Sendai National College of Technology, and with the aid of Tohoku University Global COE Program “Weaving Science Web beyond Particle-Matter Hierarchy" and a Grant-in-Aid for Scientific Research from Japan Society for the Promotion of Science (JSPS). The results have been published online in “Physical Review Letters” on December 22, 2009. The paper’s title is - Dynamical coupling and separation of multiple degrees of freedom in a photoexcited._

[Contact]
Associate Professor Sumio Ishihara
Department of Physics, Tohoku University
Tel: +81-22-795-6436