Exploration and Applied Engineering of Novel Functions Based on Nanostructures in Transparent Oxides (FY2004-2009)

ERATO Hideo Hosono (Professor, Tokyo Institute of Technology)

Discovery of new functions hidden in unexplored materials
Creation of new types of high-temperature superconductor
LaFeAsO (Iron-oxypnictide) Transition temperature = 32K (11% of O replaced by F)

Research Overview
New functional materials that outstrip conventional concepts and physical properties are sought by testing various combinations encompassing constituent elements of oxides and related compounds. It has been discovered that materials containing magnetic elements exhibit superconductivity at high temperatures. This search for a new superconductor family has received global attention.

Impact of Research Achievements
■ It has been discovered that LaFeAsO (an oxypnictide compound) whose oxygen atoms are partially replaced with fluorine atoms becomes a high-temperature superconductor with a maximum transition temperature of 32K.
■ This is a third-category high-temperature superconductor (a compound containing Fe), and is different from common metallic materials and cuprate materials.
■ No other compounds containing Fe have been confirmed to exhibit such high transition temperatures, and this discovery is believed to be a new type of high-temperature superconductor.
■ LaFeAsO holds vast potential for the exploration of new materials and has properties different from those of cuprate materials. Accordingly, further improvement in its material characteristics is expected. Research in this area has been very active, as exemplified by a report from China stating that LaFeAsO whose La is replaced with samarium (Sm) exhibits transition temperatures exceeding 50K.