[15p-P3-1~32] 6.3 酸化物エレクトロニクス

▲ [15p-P3-3] Hidden Electronic Phase Boundary in the SrTiO₃−SrNbO₃ Solid-solution System

〇(B)Yuqiao Zhang¹、Takayoshi Katase¹、Takaki Onozato¹、Bin Feng²、Hiroyuki Hayashi³、Tetsuya Tohei²、Isao Tanaka³、Yuichi Ikuhara²、Hiromichi Ohta¹ (1.Hokkaido Univ.、2.Univ. Tokyo、3.Kyoto Univ.)

キーワード：SrTiO3-SrNbO3 solid solution, electronic phase boundary, thermopower

Various physical properties of transition metal oxides (TMOs) are strongly correlated to their electronic phase, which can be controlled by changing the valence state of TM ions. Among many TMOs, strontium titanate−strontium niobate solid-solution (SrTi_1–xNb_xO₃ ss.) system, so-called Nb-doped SrTiO₃, is one of the most classic TMOs. There should be an electronic phase boundary (EPB) in the system; valence state of Ti ion is basically 4+ in SrTiO₃ crystal, but it changes into 3+ when Nb⁵⁺ ion is substituted to the neighboring Ti ion. On the other hand, that of Nb ions is basically 4+ in SrNbO₃ crystal and is unchanged when Ti ion is substituted to the neighboring Nb ion. Here we report on detection method of the hidden EPB. We measured thermopower of the SrTi_1–xNb_xO₃ ss. epitaxial films together with the Hall mobility because thermopower is insensitive to the crystal quality though Hall mobility is very sensitive. We observed clear discontinuity in the x-dependence of thermopower together with Hall mobility in between x=0.5 and 0.6 (Figure).