Multiferroicity in an organic charge-transfer salt that is suggestive of electric-dipole-driven magnetism
Multiferroicity in an organic charge-transfer salt that is suggestive of electric-dipole-driven magnetism
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DOI：
10.1038/nmat3400
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发表时间：
2012-09-01
期刊：
影响因子：
41.2
通讯作者：
Lang, Michael
中科院分区：
文献类型：
--
作者：
Lunkenheimer, Peter;Mueller, Jens;Lang, Michael
多铁性，显示电和磁的自由度的同时有序，是显着的材料，从学术和技术的角度来看（1，2）。多铁性的一个突出机制是自旋驱动的铁电性，通常在具有螺旋自旋序的受抑反铁磁体中发现（1，3 -5）。在那里，与传统的铁电体一样，电偶极子是由离子的偏心位移引起的。然而，最近一种不同的机制，即纯电子铁电性，其中电荷顺序打破反转对称性，引起了相当大的兴趣（6）。在这里，我们提供了铁电性的证据，伴随着反铁磁自旋顺序，在一个二维的有机电荷转移盐，从而代表了一类新的多铁性。我们提出了一个电荷顺序驱动的机制，导致电子铁电性在这种材料。对于电子铁电体，偶极和自旋序几乎同时出现。这可以归因于铁电有序引起的自旋阻挫的损失。因此，这里的自旋序是由铁电性驱动的，与螺旋磁体中的自旋驱动铁电性形成鲜明对比。
Multiferroics, showing simultaneous ordering of electrical and magnetic degrees of freedom, are remarkable materials as seen from both the academic and technological points of view(1,2). A prominent mechanism of multiferroicity is the spin-driven ferroelectricity, often found in frustrated antiferromagnets with helical spin order(1,3-5). There, as for conventional ferroelectrics, the electrical dipoles arise from an off-centre displacement of ions. However, recently a different mechanism, namely purely electronic ferroelectricity, where charge order breaks inversion symmetry, has attracted considerable interest(6). Here we provide evidence for ferroelectricity, accompanied by antiferromagnetic spin order, in a two-dimensional organic charge-transfer salt, thus representing a new class of multiferroics. We propose a charge-order-driven mechanism leading to electronic ferroelectricity in this material. Quite unexpectedly for electronic ferroelectrics, dipolar and spin order arise nearly simultaneously. This can be ascribed to the loss of spin frustration induced by the ferroelectric ordering. Hence, here the spin order is driven by the ferroelectricity, in marked contrast to the spin-driven ferroelectricity in helical magnets.