| Research Abstract |
We have grown the new quasi one- and two-dimensional magnet, VOMoOィイD24ィエD2 and (VィイD20.56ィエD2, MoィイD20.44ィエD2)ィイD22ィエD2OィイD25ィエD2. Their simultaneous measurement of magnetic, electrical and optical properties was performed. Here the relation between the crystal instability, unstable quantum state, and the fluctuation of internal magnetic field was discussed. That instability brings a characteristic temperature dependent behavior into the scattering process of electrons, hence into the electrical conductivity. Separately we have found a crystal substituted by tellurium, TeィイD24ィエD2MoィイD220ィエD2OィイD262ィエD2, that shows a two-dimensional electrical conductivity. Compounds with the same crystal structure, BiィイD24ィエD2MoィイD220ィエD2OィイD262ィエD2 and SbィイD24ィエD2MoィイD220ィエD2OィイD262ィエD2 are already known, but both have been synthesized only in the powder form. We have also found the way of crystal growth for the later two compounds. Previous workers found that the carriers in BiィイD24ィエD2MoィイD220ィエD2
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OィイD262ィエD2 and SbィイD24ィエD2MoィイD220ィエD2OィイD262ィエD2 change the sign in the lower temperature region. The present new telluride is contrary a p-type semiconductor. We are considering substituting more metal ions such as lead, or mixed two metal ions. Then we expect to control the sign and the mobility of carriers. Moreover, we measured the specific heat of η-MoィイD24ィエD2OィイD211ィエD2 with an improved precision. In KィイD20.3ィエD2MoOィイD23ィエD2 we discover the TィイD15ィエD1 dependent behavior of the electrical conductivity in the metallic region.
In the second, the study of application somewhat overlap with the above description. Compound MィイD24ィエD2MoィイD220ィエD2OィイD262ィエD2 is constructed from the flame of molybdenum oxides, where the hexagonal tube like caves distribute in an ordered manner. The caves capture many kinds of charge carriers, M. The flame is stable even if the M is absent, so M should be free to come in and out. We intended to select the dopant considering the electro-negativity. For VOMoOィイD24ィエD2 we have also succeeded to dope potassium by using KィイD22ィエD2MoOィイD24ィエD2. All the examination is left to the near future. Less
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