Abstract

The spin states of Co atoms in PrBaCo₂O_{5 + δ} with regard to the paramagnetic contribution of Pr³⁺ ions have been determined from magnetic property studies for δ = 0.52 and 0.74. Results obtained without considering the paramagnetic contribution of Pr³⁺ ions are inconsistent with available experimental data. With a decrease in temperature, the metal–insulator transition in PrBaCo₂O_5.52 becomes sharper according to a sharp change in spin states (from HS/LS to LS/IS) of Co³⁺ ions. In this case, Co³⁺ ions occupying octahedra pass from the high-spin state (HS, S = 2) to the low-spin one (LS, S = 0) and those occupying pyramids pass from the LS-state to the intermediate spin state (IS, S = 1), as follows from the available structural data. In PrBaCo₂O_5.74, the metal–semiconductor transition occurs smoothly from HS/LS to the HS/IS state upon the smooth transition of the Co³⁺ ion state from (LS, S = 0) to the (IS, S = 1) state in pyramides without change in the spin state of ions Co³⁺ (HS, S = 2) and Co⁴⁺ (LS, S = 1/2) in octahedrons.

中文翻译：

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层状钴矿中钴离子的自旋态和金属-半导体转变 PrBaCo2O5 + δ (δ = 0.52, 0.74)

摘要

_{PrBaCo 2} O _{5 + δ}中 Co 原子的自旋态相对于 Pr ³⁺离子的顺磁贡献已通过 δ = 0.52 和 0.74 的磁特性研究确定。^{在不考虑 Pr 3+}离子的顺磁贡献的情况下获得的结果与现有的实验数据不一致。随着温度的降低，PrBaCo ₂ O _5.52中的金属-绝缘体转变由于Co ³⁺离子自旋态的急剧变化（从HS/LS 到LS/IS）而变得更加尖锐。在这种情况下，占据八面体的 Co ³⁺离子从高自旋态（HS，S = 2）传递到低自旋态（LS，S = 0），而占据金字塔的那些离子从 LS 态传递到中间态自旋态（IS，S = 1），根据可用的结构数据如下。在 PrBaCo ₂ O _{5.74中，当 Co} ³⁺离子态从 (LS, S = 0) 平稳过渡到 (IS, S = 1 )时，金属-半导体从 HS/LS 平稳过渡到 HS/IS 态。 ) 金字塔中的状态，八面体中离子 Co ³⁺ (HS, S = 2) 和 Co ⁴⁺ (LS, S = 1/2)的自旋状态没有变化。