Abstract Ruddlesden-Popper (RP) La2−xSrxCoO4 (x = 0.7, 0.9, 1.1, 1.3) were synthesized by a modified sol-gel route. The synthesized samples were characterized by XRD, FE-SEM technique, iodometric titration, FT-FIR spectroscopy and VSM analysis. The variation of Co-O bond length obtained from Rietveld refinements and the related peak shifts in the FT-FIR spectra showed that Co3+ has both LS and IS spin states. It is found that the population of Co3+ in the LS state decreases and IS state increases with increasing Sr concentration. Jahn-Teller effect was identified in the FT-FIR absorption bands, corresponding to the vibration modes of Co bonds with the apical and equatorial oxygen atoms. The ferromagnetic characteristic of La0.7Sr1.3CoO4, obtained by VSM, revealed the increase of Co3+ IS population by Sr doping, in agreement with XRD and FT-FIR results. The shift and split of the IR absorption bands with the change in the structural parameters are proposed to be an applicable tool to probe the spin states and Jahn-Teller effect in La2−xSrxCoO4 compounds.

中文翻译：

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Ruddlesden-Popper La 2-x Sr x CoO 4 的钴自旋态研究，使用 X 射线衍射和红外光谱

摘要 Ruddlesden-Popper (RP) La2−xSrxCoO4 (x = 0.7, 0.9, 1.1, 1.3) 通过改进的溶胶-凝胶路线合成。通过XRD、FE-SEM技术、碘量滴定、FT-FIR光谱和VSM分析对合成的样品进行表征。从 Rietveld 精修获得的 Co-O 键长的变化和 FT-FIR 光谱中的相关峰位移表明 Co3+ 具有 LS 和 IS 自旋态。发现随着Sr浓度的增加，LS态Co3+的数量减少，IS态增加。在 FT-FIR 吸收带中发现了 Jahn-Teller 效应，对应于 Co 键与顶端和赤道氧原子的振动模式。通过 VSM 获得的 La0.7Sr1.3CoO4 的铁磁特性揭示了 Sr 掺杂导致 Co3+ IS 数量增加，与 XRD 和 FT-FIR 结果一致。随着结构参数的变化，红外吸收带的移动和分裂被认为是探测 La2−xSrxCoO4 化合物中的自旋态和 Jahn-Teller 效应的适用工具。