Broken magnetic symmetry due to charge-order ferroelectricity discovered in (TMTTF) 2 X salts by multifrequency ESR
Broken magnetic symmetry due to charge-order ferroelectricity discovered in (TMTTF) 2 X salts by multifrequency ESR
复制标题
通过多频 ESR 在 (TMTTF) 2 X 盐中发现电荷级铁电性导致的磁对称性破坏
DOI：
10.1103/physrevb.85.144428
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发表时间：
2012
影响因子：
3.7
通讯作者：
M. Dressel
中科院分区：
文献类型：
--
作者：
S. Yasin;B. Salameh;E. Rose;M. Dumm;H.-A. Krug von Nidda;A. Loidl;M. Ozerov;G. Untereiner;L.K. Montgomery;M. Dressel
通过对K的电子自旋共振（ESR）实验，研究了准一维有机电荷转移盐（TMTTF）（TMTTF代表四甲基四硫富瓦烯，AsF，SbF和SCN）的电荷有序态.在升高的温度下，所有化合物都显示出线性增加。在电荷有序转变以下，在ESR谱线宽度的温度依赖性和各向异性方面都观察到重要的异常。在中心对称阴离子PF，AsF和SbF的情况下，当在垂直于分子轴的平面内旋转时，线宽加倍其周期性;并且它表现出显着的频率依赖性。这种增强的线宽是由各向异性塞曼相互作用，我们确定为一个弛豫过程中的电荷有序状态，磁不等价的网站存在于相邻的堆栈。因此，电荷有序不仅产生铁电性，而且打破了这些有机量子自旋链中磁自由度的对称性。对于（TMTTF）SCN电荷顺序与非中心对称阴离子的顺序相一致，偶极相互作用的大贡献占主导地位的弛豫过程。
We have investigated the charge-ordered state of the quasi-one-dimensional organic charge-transfer salts (TMTTF)(where TMTTF stands for tetramethyltetrathiafulvalene andAsF, SbF, and SCN) by performing comprehensive electron-spin-resonance (ESR) experiments at several frequencies forK. At elevated temperatures all compounds show a linear increase of. Below the charge-ordering transitionimportant anomalies are observed in both the temperature dependence and the anisotropy of the ESR linewidth. In the case of the centrosymmetric anions PF, AsF, and SbF, the linewidth doubles its periodicity when rotated in a plane normal to the molecule axis; and it exhibits a significant frequency dependence. This enhanced linewidth is caused by anisotropic Zeeman interaction that we identify as a relaxation process in the charge-ordered state where magnetically inequivalent sites are present in adjacent stacks. Thus, charge order not only produces ferroelectricity but also breaks the symmetry of the magnetic degree of freedom in these organic quantum spin chains. For (TMTTF)SCN charge order coincides with the ordering of the non-centrosymmetric anions; the large contribution of dipolar interaction dominates the relaxation process.