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Structural properties and phase transition of hole-orbital-ordered (C$$_{2}$$H$$_{5}$$NH$$_{3}$$)$$_{2}$$CuCl$$_{4}$$ studied by resonant and non-resonant X-ray scatterings under high pressure

高圧下共鳴,非共鳴X線散乱実験によるホール軌道秩序物質(C$$_{2}$$H$$_{5}$$NH$$_{3}$$)$$_{2}$$CuCl$$_{4}$$の構造特性と相転移の研究

大和田 謙二; 石井 賢司; 稲見 俊哉; 村上 洋一; 菖蒲 敬久*; 大隅 寛之*; 池田 直*; 大石 泰生*

Owada, Kenji; Ishii, Kenji; Inami, Toshiya; Murakami, Yoichi; Shobu, Takahisa*; Osumi, Hiroyuki*; Ikeda, Naoshi*; Oishi, Yasuo*

構造とそれに関係する共鳴X線散乱(RXS)の圧力効果がホール軌道秩序物質(C$$_{2}$$H$$_{5}$$NH$$_{3}$$)$$_{2}$$CuCl$$_{4}$$において調べられた。ラマン散乱によって示唆されたPc=4GPaの相転移が斜方晶-単斜晶相転移に伴うピークスプリットから直接観測された。ヤーンテラー歪みの圧力による減少を構造解析から明らかにした。それに伴い、黄色い結晶は赤に赤方変移することが顕微鏡観察で確認した。また、われわれはRXS強度の起源が3d-4pクーロン相互作用の結果ではなく、八面体歪みを感じた4p軌道の分極であることを突き止めた。高圧下でのRXSが調べられたが、Pcまでに強度の変化は余りなく、Pc以上で急激に強度がなくなることが観測された。これに伴いPc以上での2つの可能な構造が提案された。

The effects of hydrostatic pressure on a structure and the corresponding resonant X-ray scattering (RXS) spectrum have been investigated for the hole-orbital-ordered compound (C$$_{2}$$H$$_{5}$$NH$$_{3}$$)$$_{2}$$CuCl$$_{4}$$. We have found a structural phase transition at Pc=4 GPa. The reduction of the Jahn-Teller distortion (JTD) toward Pc is also ascertained by structural analyses. The gradual change in the color of the crystal is also observed in connection with the structural change near Pc. We experimentally confirmed that the RXS intensity comes from the polarization of the density of states of px and py symmetries, which is mainly dominated not by the on-site 3d-4p Coulomb interaction but by the JTD of the CuCl$$_{6}$$ octahedron. The RXS study under a high pressure shows no striking change as JTD is suppressed by the application of pressure. On the other hand, the RXS intensity becomes zero above Pc. The results indicate that the local environment of the Cu$$^{2+}$$ ion markedly changes. Two possible structures above Pc are proposed.

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パーセンタイル:67.58

分野:Materials Science, Multidisciplinary

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