JAPAN NANONET BULLETIN - 8th Issue - December 25, 2003

YOUNG RESEARCHERS’ INTRODUCTION

Takao MORI Senior Researcher , Advanced Materials Laboratory, National Institute for Materials Science Researcher, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST) 1996 Ph.D. Faculty of Science, The University of Tokyo 1996 Postdoctoral Researcher, Dept. of Applied Physics, Faculty of Engineering, The University of Tokyo 1998 Researcher, National Institute for Research in Inorganic Materials 2001 Researcher, National Institute for Materials Science 2001 Researcher, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency(JST) 2003 Senior Researcher, National Institute for Materials Science E-mail address:

This research is focused on finding new ways of discovering and developing functionalities in boron-based network compounds (cluster compounds and 2 dimensional-[BC]-net-containing compounds) of which physical properties are largely dependent on structural order, and which have not been as well studied as their carbon counterparts.

We work on synthesis and physical property control of cluster compounds with an ordered boron-cluster lattice structure, into which metal atoms have been inserted in order to induce new magnetic and optical properties. We have discovered that the B12 clusters are a completely new mediator of magnetic interaction, and new magnetic components containing the boron icosahedra are being developed. We have also clarified that the high-temperature ferromagnetism (as reported in Nature and Science) in boron compounds such as hole-doped CaB6, is actually not intrinsic and results from an impurity effect. We now are developing compounds in which Er atoms are inserted into a semiconducting boron-cluster lattice and the compounds exhibit photoluminescence properties in the wavelength range of 1.5 μm, where they have the least transmission loss in optical fibers.

Furthermore, we are studying the 2-dimensionality of [BC]-net-containing compounds to realize attractive physical properties. We have discovered the first graphite intercalation compound (GIC) with mixed boron and carbon [BC] layers and are trying to apply this compound to new battery materials. The MgB2-related MgB2C2 compound is also being studied in an attempt to induce high TC superconductivity through hole-doping, and so far we have been successful in inducing a semiconductor-to-metal transition by substituting Li for Mg.

Fig. 1 The structure and magnetic properties of the higher boride with a TbB50 structure, in which we discovered the first magnetic transition. B12 icosahedra were found to be a new mediator of magnetic interaction. Up to now, 7 B12-icosahedra-containing-systems have been found to exhibit magnetic transitions.

Fig. 2 The [B/C] layered compound MgB2C2 has a flat band along the T-Y direction, which is similar to the Γ-A band in MgB2. Two methods of hole-doping are attempted to induce high TC superconductivity.