Stability of the Cationic Oxidation States in Pr0.50Sr0.50CoO3 across the Magnetostructural Transition by X-ray Absorption Spectroscopy

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• 作者：Jessica Padilla-Pantoja ; Javier Herrero-Mart铆n ; Pierluigi Gargiani ; S. Manuel Valvidares ; Vera Cuartero ; Kurt Kummer ; Oliver Watson ; Nicholas B. Brookes ; Jos茅 Luis Garc铆a-Mu帽oz
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：September 2, 2014
• 年：2014
• 卷：53
• 期：17
• 页码：8854-8858
• 全文大小：343K
• ISSN：1520-510X

文摘

The possible hybridization between Pr 4f and O 2p states in Pr_0.50Sr_0.50CoO₃ at low temperatures was investigated by different techniques. First, using neutron diffraction we observed a strong contraction of some Pr鈥揙 bonds across the magnetostructural transition at T_S 鈭?120 K. In contrast to the Pr鈥揙 bond contraction in Pr_0.50Ca_0.50CoO₃, this transition is not accompanied by the appearance of Pr⁴⁺ at low temperatures, as revealed by X-ray absorption spectroscopy at Pr edges. Despite the fact that a Pr valence change is not the mechanism that drives this transition, we point out an active participation of Pr ions across T_S. Moreover, Co L_2,3-edge and O K edge X-ray absorption spectra did not reveal any spin-state variation and showed the stability of the average formal valence of cobalt ions. The large density of empty t_2g symmetry states in the studied thermal range does not suggest the occurrence of Co³⁺ in a pure low-spin state. The overall metallic behavior agrees with our findings. We propose a mixture of Co³⁺ ions in the intermediate-spin or high-spin configuration together with Co⁴⁺ ions in a low- or intermediate-spin state.