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Domain boundary in multi-FERROIC materials

多铁性材料中的磁畴边界

基本信息

批准号：
EP/K009702/1
负责人：
Ekhard Salje
金额：
$ 28.15万
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FK009702%2F1
关键词：
Domain boundary multi FERROIC materials

项目摘要

The propagation of magnetic domain walls in a nanowire is already used as a memory device today: each time a domain wall passes a pick-up coil, a signal is emitted and encoded. The same technology does not apparently work in ferroelectric or ferroelastic domain walls because the movement of the wall is much less smooth: it can 'jerk' and emit spontaneously acoustic or electric signals. These signals are unwanted and lead to 'noise' in any device application. This limitation is not a physical necessity, though. Smooth movements are seen in ferroelastic SrTiO3 while most porous materials are almost totally 'jerky' and form avalanches of domain walls which can not be controlled in any device application. The first aim of the proposal is to investigate the crossover between noisy and silent wall propagation.Ferroelastic and ferroelectric domain walls (they are often both) have another fantastic property: they can be changed easily by doping, they can be bent, and they can form complex domain patterns which contain much more information than can be encoded in single magnetic domain walls. Examples are superconducting domain walls in WO3, highly conducting and photovoltaic walls in BiFeO3 and polar walls in CaTiO3. All these materials are well known and can be deposited routinely as thin films on appropriate substrates. What is missing is the knowledge of the mechanism by which such walls change their local structure and how this effect changes their mobilities. Walls are very thin (1-10nm) and it is therefore extremely difficult and costly to investigate their structural properties by experimental means. We have done some of the most advanced experimental work in this field but now it has become timely to advance our research theoretically by computer simulation of the relevant domain patterns. The appropriate theory is based on complex Landau-Ginzburg theory with interacting order parameters, the computer simulation of the domain patterns is based on mechanical, non-local models of interacting local state parameters with a large number of interacting 'atoms'. Here a minimum of 1 million particles are required to see boundary effects, propagating kink excitations and mutual jamming of domain walls. We will extend this size to >10 million particles.Our second aim is hence to derive realistic thermodynamic potentials for interacting domain walls and simulate the pattern formation on a large enough scale to be realistic for possible device applications.

今天，纳米线中磁区壁的传播已经被用作存储设备：每当磁区壁经过拾取线圈时，就会发射并编码一个信号。同样的技术显然不适用于铁电或铁弹磁区，因为磁区的运动不是很平稳：它可以“猛然”并自发地发出声学或电信号。这些信号是不需要的，并且在任何设备应用中都会导致“噪声”。然而，这一限制并不是物理上的必要。在铁弹性的钛酸锶中可以看到平滑的运动，而大多数多孔材料几乎完全是‘急速’的，并形成雪崩的域壁，这在任何器件应用中都是无法控制的。该提议的第一个目的是研究有噪声和无声壁传播之间的交叉。铁弹性和铁电域壁(它们通常都是)还有另一个奇妙的性质：它们可以很容易地通过掺杂改变，它们可以弯曲，它们可以形成复杂的磁畴图案，包含的信息量比单一磁畴壁中编码的要多得多。例如WO_3中的超导磁区壁、BiFeO_3中的高导电性和光伏电壁以及CaTiO_3中的极化壁。所有这些材料都是众所周知的，并且可以常规地作为薄膜沉积在适当的衬底上。缺乏的是对这种墙改变其局部结构的机制的了解，以及这种效应如何改变它们的流动性。壁非常薄(1-10 nm)，因此通过实验手段研究其结构性质是极其困难和昂贵的。我们已经在这一领域做了一些最先进的实验工作，但现在已经到了通过计算机模拟相关领域模式来从理论上推进我们的研究的时候了。合适的理论是基于具有相互作用序参数的复Landau-Ginzburg理论，对磁畴图案的计算机模拟是基于与大量相互作用的‘原子’相互作用的局域态参数的非局域力学模型。在这里，至少需要100万个粒子才能看到边界效应、传播扭结激发和域壁的相互干扰。我们将把这个尺寸扩展到1000万个粒子。因此，我们的第二个目标是推导出相互作用的域壁的真实热力学势，并在足够大的尺度上模拟图案的形成，以便为可能的器件应用提供现实。