A Complete High-to-Low spin state Transition of Trivalent Cobalt Ion in Octahedral Symmetry in SrCo0.5Ru0.5O3-δ

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• 作者：Jin-Ming Chen ; Yi-Ying Chin ; Martin Valldor ; Zhiwei Hu ; Jenn-Min Lee ; Shu-Chih Haw ; Nozomu Hiraoka ; Hirofumi Ishii ; Chih-Wen Pao ; Ku-Ding Tsuei ; Jyh-Fu Lee ; Hong-Ji Lin ; Ling-Yun Jang ; Arata Tanaka ; Chien-Te Chen ; Liu Hao Tjeng
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：January 29, 2014
• 年：2014
• 卷：136
• 期：4
• 页码：1514-1519
• 全文大小：385K
• ISSN：1520-5126

文摘

The complex metal oxide SrCo_0.5Ru_0.5O_3-未 possesses a slightly distorted perovskite crystal structure. Its insulating nature infers a well-defined charge distribution, and the six-fold coordinated transition metals have the oxidation states +5 for ruthenium and +3 for cobalt as observed by X-ray spectroscopy. We have discovered that Co³⁺ ion is purely high-spin at room temperature, which is unique for a Co³⁺ in an octahedral oxygen surrounding. We attribute this to the crystal field interaction being weaker than the Hund鈥檚-rule exchange due to a relatively large mean Co鈥揙 distances of 1.98(2) 脜, as obtained by EXAFS and X-ray diffraction experiments. A gradual high-to-low spin state transition is completed by applying high hydrostatic pressure of up to 40 GPa. Across this spin state transition, the Co K尾 emission spectra can be fully explained by a weighted sum of the high-spin and low-spin spectra. Thereby is the much debated intermediate spin state of Co³⁺ absent in this material. These results allow us to draw an energy diagram depicting relative stabilities of the high-, intermediate-, and low-spin states as functions of the metal鈥搊xygen bond length for a Co³⁺ ion in an octahedral coordination.