Thermodynamics of the spin transition in [FexZn1-x(2-pic)3]Cl2.EtOH
Thermodynamics of the spin transition in [FexZn1-x(2-pic)3]Cl2.EtOH
复制标题
[FexZn1-x(2-pic)3]Cl2.EtOH 中自旋跃迁的热力学
DOI：
10.1016/0022-3697(92)90055-i
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发表时间：
1992
影响因子：
4
通讯作者：
P. Gütlich
中科院分区：
文献类型：
--
作者：
R. Jakobi;H. Spiering;P. Gütlich
用新型量热计重新研究了[FexZn 1 −x（2-pic）3] Cl 2· EtOH混晶在15 ~ 300 K温度范围内的比热Cp。在唯象热力学模型的基础上，混晶（x= 0.73）Cp（T）曲线的反常可以定量地描述为自旋跃迁（1A 1（低自旋，LS）→ 5 T2（高自旋，HS））的结果。吉布斯自由能的参数独立地从[FexZn 1 −x（2-pic）3] Cl 2· EtOH中HS分数γ的温度依赖性导出。纯铁配合物（x= 1）表现出两步自旋跃迁。在这两个步骤之间的温度范围内，从Cp值获得的熵低于从晶体中HS和LS络合物的随机混合物获得的熵。这种熵的减少被解释为HS和LS分子的排序。
With a new type of calorimeter we reinvestigated the specific heatCpof the mixed crystals [FexZni1−x(2-pic)3]Cl2· EtOH in the temperature range from 15 to 300 K. On the basis of a phenomenological thermodynamic model the anomaly in theCp(T) curve of the mixed crystal (x= 0.73) can be quantitatively described as a result of the spin transition (1A1(low spin, LS) →5T2(high spin, HS)). The parameters of the Gibbs free energy were independently derived from the temperature dependence of the HS fraction γ in [FexZn1−x(2-pic)3]Cl2· EtOH. The pure iron complex (x= 1) exhibits a two-step spin transition. In the temperature range between the two steps the entropy obtained from theCpvalues is lower than expected from a random mixture of HS and LS complexes in the crystal. This reduction of entropy is interpreted in terms of an ordering of HS and LS molecules.