Division of Materials Physics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Nat Commun. 2013;4:2063. doi: 10.1038/ncomms3063.
The glass state of matter represents a frozen state of an atomically disordered system with local order only. Instead of atoms, systems with glassy states of magnetic and electric dipole moments in solids are known as spin and dipole glasses, respectively. In these conventional glasses, slow dynamics, such as relaxation and memory phenomena, are characteristics of their magnetic/dielectric properties. Here we propose a new glassy state in solids, a 'toroidal glass', in which toroidal moments-vector-like electromagnetic multipole moments breaking both space inversion and time reversal symmetries, and producing a linear magnetoelectric coupling-are randomly oriented and frozen. We investigate the dynamics of a linear magnetoelectric effect in Ni0.4Mn0.6TiO3 and find that the magnetoelectric responses strongly depend on the magnetoelectric cooling history and show striking memory effects. These unusual magnetoelectric dynamical features can be explained in the framework of a toroidal glass in which the toroidal frozen state can be controlled magnetoelectrically.
物质的玻璃态代表了一种原子无序系统的冻结状态，只有局部有序。在固体中，具有磁和电偶极矩玻璃态的系统分别被称为自旋玻璃和偶极玻璃。在这些常规玻璃中，弛豫和记忆等缓慢动力学是其磁/电性质的特征。在这里，我们在固体中提出了一种新的玻璃态，即“环形玻璃”，其中环形矩——打破空间反演和时间反演对称性并产生线性磁电耦合的矢量状电磁多极矩——随机取向并冻结。我们研究了 Ni0.4Mn0.6TiO3 中的线性磁电效应的动力学，发现磁电响应强烈依赖于磁电冷却历史，并表现出显著的记忆效应。这些异常的磁电动力学特征可以在环形玻璃的框架内得到解释，其中环形冻结状态可以通过磁电控制。
