EXCHANGE INTERACTIONS, CHARGE DELOCALIZATION, AND SPIN RELAXATION IN A MIXED-VALENCE DIIRON COMPLEX STUDIED BY MOSSBAUER-SPECTROSCOPY
EXCHANGE INTERACTIONS, CHARGE DELOCALIZATION, AND SPIN RELAXATION IN A MIXED-VALENCE DIIRON COMPLEX STUDIED BY MOSSBAUER-SPECTROSCOPY
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DOI：
10.1063/1.465881
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发表时间：
1993-11-01
影响因子：
4.4
通讯作者：
GIBSON, JF
中科院分区：
文献类型：
--
作者：
DING, XQ;BILL, E;GIBSON, JF
利用穆斯堡尔谱分析研究了混合价态[Fe2S2（二甲基甲烷双苯并咪唑盐）2]3-三阴离子Fe2+Fe3+在1.5 ~ 180 K温度范围内，在10 mT， 0.35 T，和6.2 t.低温光谱显示了总自旋S(t) = 1/2的基态，超精细参数介于Fe2+Fe3+定域混合价对和两个铁原子等效的完全离域体系之间。考虑到S(t) = 1/2态的自旋弛豫和铁离子间的电子跳变，用随机弛豫模型拟合光谱，得到了一组一致的超精细参数。通过求解自旋哈密顿量给出了超精细参数值的解释，其中包括不对称Fe2+Fe3+对中的反铁磁和双交换，并允许部分电子离域。使用价值a2移位系数= 0.8,估计δ= 105 cm - 1 S (t) = 1/2的区别和第一兴奋S (t) = 3/2状态限制派生交换耦合常数J,双重交换参数B, E和能量差(A) - E (B)由两种可能的配置Fe (A) 2 +铁(B) 3 +和Fe (A) 3 +铁(B) 2 +,也就是说,70 cm - 1小于或类似于J小于300 cm - 1类似,0 < B的绝对值小于或类似于395 cm-1, 0 < \E(A) - E(B)\小于或类似于590 cm-1。
Exchange interactions and charge transfer in the Fe2+Fe3+ of the mixed valence [Fe2S2 (dimethylmethanebisbenzimidazolate)2]3- trianion have been studied by analysis of Mossbauer spectra in the temperature range of 1.5-180 K and in applied fields of 10 mT, 0.35 T, and 6.2 T. The low-temperature spectra reveal a ground state with total spin S(t) = 1/2 and hyperfine parameters intermediate between values for a Fe2+Fe3+ localized mixed-valence pair and a fully delocalized system where the two iron atoms are equivalent. A consistent set of hyperfine parameters has been derived by fitting the spectra with a stochastic relaxation model taking into account spin relaxation in the S(t) = 1/2 state and electron hopping between the iron ions. An interpretation of the values of the hyperfine parameters has been given by solving a spin Hamiltonian, which includes antiferromagnetic and double exchange in an asymmetric Fe2+Fe3+ pair and which allows partial electron delocalization. Using the value a2 = 0.8 for the delocalization coefficient and an estimate of DELTA = 105 cm-1 for the difference between the S(t) = 1/2 and the first excited S(t) = 3/2 state we have derived limits for the exchange-coupling constant J, the double-exchange parameter B, and the energy difference E(A) - E(B) arising from the two possible configurations Fe(A)2+Fe(B)3+ and Fe(A)3+Fe(B)2+, i.e., 70 cm-1 less than or similar to J less than or similar to 300 cm-1, 0 < Absolute value of B less than or similar to 395 cm-1, and 0 < \E(A) - E(B)\ less than or similar to 590 cm-1.