Relaxor ferroelectricity and colossal magnetocapacitive coupling in ferromagnetic CdCr2S4
Relaxor ferroelectricity and colossal magnetocapacitive coupling in ferromagnetic CdCr2S4
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DOI：
10.1038/nature03348
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发表时间：
2005-03-17
期刊：
影响因子：
64.8
通讯作者：
Loidl, A
中科院分区：
文献类型：
--
作者：
Hemberger, J;Lunkenheimer, P;Loidl, A
磁序和电序共存的材料--称为“多铁性”或“磁电性”--最近已成为许多研究的焦点[1-4]。特别是，铁磁性和铁电性的同时发生，以及通过磁容效应实现的磁化和极化的紧密耦合，为新一代电子设备带来了希望。在这里，我们介绍了一种简单的立方尖晶石化合物的测量结果，它具有不同寻常的和潜在的有用的磁性和电学性质：它显示出铁磁有序和弛豫铁电性共存(具有弥散相变的铁电团簇状态)，两者都具有相当大的有序化温度和矩。在接近铁磁有序温度时，磁容耦合(其特征是介电常数在外部磁场中的变化)达到巨大的值，接近500%。我们将弛豫特性归因于几何受挫，几何受挫是众所周知的磁矩，但这里发现阻碍了驱动铁电态形成的结构自由度的长程有序。
Materials in which magnetic and electric order coexist - termed 'multiferroics' or 'magnetoelectrics' - have recently become the focus of much research(1-4). In particular, the simultaneous occurrence of ferromagnetism and ferroelectricity, combined with an intimate coupling of magnetization and polarization via magnetocapacitive effects, holds promise for new generations of electronic devices. Here we present measurements on a simple cubic spinel compound with unusual, and potentially useful, magnetic and electric properties: it shows ferromagnetic order coexisting with relaxor ferroelectricity ( a ferroelectric cluster state with a smeared-out phase transition), both having sizable ordering temperatures and moments. Close to the ferromagnetic ordering temperature, the magnetocapacitive coupling ( characterized by a variation of the dielectric constant in an external magnetic field) reaches colossal values, approaching 500 per cent. We attribute the relaxor properties to geometric frustration, which is well known for magnetic moments but here is found to impede long-range order of the structural degrees of freedom that drive the formation of the ferroelectric state.