High pressure synthesis and physical properties of rare earth borides with a cage like

本研究的目的是利用高压合成技术（最高压力= 10 GPa，最高温度=1800℃）合成目前在常压下无法合成的RB_6和RB_<12>（R=La &lt;$Yb）稀土硼化物材料。通过对磁性、输运、热性质等的测量，有望发现许多有趣的行为，如价态涨落、近藤效应、近藤半导体、多极有序和新的磁有序，研究代表伊加介绍了一种桌面型的高-在最高温度1800℃、最高压力4GPa的条件下，伊加试图进行GdB_的高压合成<12>。高压合成的最佳条件尚未确定。另外，该设备也可用于笼形化合物和方钴矿化合物的合成。伊加和研究合作者山中教授尝试<12>使用Cubic-ambil设备在1600℃和5GPa压力下约1小时的条件下进行GdB_的高压合成。X射线衍射分析表明，GdB_6和GdB_2<12>以1：1的比例形成两相。此外，去年我们还尝试在10 GPa和1500℃下进行更高压力的合成。为了获得单相的GdB_1，将八面体ambil包括在Cubic-ambil中<12>。该方法由Yamanaka教授开发。目前正在不断寻找更好的条件。

The purpose of this research is synthesis of materials that cannot be synthesized up to now under ambient pressure by the technique of a high-pressure synthesis (highest pressure= 10GPa, maximum temperature=1800℃) among rare earth borides of RB_6 and RB_<12> (R=La〜Yb). Many interesting behaviors such as valence fluctuation, Kondo effect, Kondo semiconductor, multipole ordering and new magnetic ordering will be expected to be found from the measurements of magnetism, transport, thermal properties, and the electronic structure by the optical spectroscopy.Research representative's Iga introduced a desk-top type high-pressure synthetic equipment under the condition of the maximum temperature 1800℃ and highest pressure 4GPa. Iga tried to do a high-pressure synthesis of GdB_<12>. The optimum condition for high pressure synthesis is not yet established. Otherwise, this equipment is useful for synthesis of clathrate and skutterdite compounds.Iga and the research collaborator Prof.Yamanaka tried to do a high pressure synthesis of GdB_<12> by using a Cubic-ambil equipment under the condition of about one hour at 1600℃ at pressure of 5GPa. X-ray analysis clarified that two phases of GdB_6 and GdB_<12> were formed in the ratio of 1:1. Furthermore we tried to do higher pressure synthesis at 10GPa and 1500℃ at last year. Octahedral ambil was included in Cubic-ambil in order to obtain the single phase of GdB_<12>. This method was developed by Prof.Yamanaka. At present the better condition is continuously searched.