Selective spin-state switch and metal-insulator transition in GdBaCo2O5.5
Selective spin-state switch and metal-insulator transition in GdBaCo2O5.5
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DOI：
10.1103/physrevb.65.180405
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发表时间：
2002-03
影响因子：
3.7
通讯作者：
C. Frontera;J. L. Garc'ia-Munoz;A. Llobet;M. Aranda
中科院分区：
文献类型：
--
作者：
C. Frontera;J. L. Garc'ia-Munoz;A. Llobet;M. Aranda
gdbaco2o5的超高分辨同步加速器衍射数据。对co3 + ba -钴酸盐的金属-绝缘体转变有了新的认识。相变加热时，coco6八面体呈异常膨胀，而coco5锥体在间隙闭合时呈正常收缩。绝缘体到金属的转变是由于八面体中的一些电子（t6 2g态）突然激发到Co e g带（最终t4 2g态）。金字塔中的t52g1g态没有改变，结构研究也排除了在tmi处的d3x2r2 / d3y2 - r2轨道顺序。
Ultrahigh resolution synchrotron diffraction data for GdBaCo 2 O 5 . 5 throw new light on the metal-insulator transition of Co 3 + Ba-cobaltites. An anomalous expansion of CoO 6 octahedra is observed at the phase transitionon heating, while CoO 5 pyramids show the normal shrinking at the closing of the gap. The insulator-to-metal transition is attributed to a sudden excitation of some electrons in the octahedra (t 6 2 g state) into the Co e g band (final t 4 2 g e 2 g state). The t 5 2 g e 1 g state in the pyramids does not change and the structural study also rules out a d 3 x 2 r 2 /d 3 y 2 - r 2 orbital ordering at T M I .