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Three-Dimensional Artificial Spin-Ice

三维人工旋转冰

基本信息

批准号：
EP/L006669/1
负责人：
Sam Ladak
金额：
$ 11.13万
依托单位：
CARDIFF UNIVERSITY
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%2FL006669%2F1
关键词：
Three Dimensional Artificial Spin Ice

项目摘要

Frustration is when the pairwise interactions within a system cannot be simultaneously satisfied and the phenomena is important in explaining a diverse range of phenomena, from the production of solar flares to bonding within water-ice. In order to study frustration, physicists look for ideal systems where the interaction between physical elements, such as spin, can be directly probed via experiment. One such condensed matter system that has recently been subject of intense study is the spin-ice materials. These are bulk crystals where spins are located on the corners of joint tetrahedra. There are four spins per tetrahedra, and each of these can point either into or out from the centre of the tetrahedron. The spins, which would like to sit head-to-tail with each of their neighbours, are frustrated and this leads to a minimum energy configuration known as the ice-rules where two spins point into the centre of the tetrahedra and two spins point out. Flipping a single spin on a tetrahedron leads to an ice-rule violating defect with finite magnetic charge in the centre. These defects interact via a magnetic equivalent to Coulombs law and are magnetic monopoles in the vector fields M and H. The realisation of monopoles in spin-ice is exciting and has lead to a new field where the movement of magnetic charges (Magnetricity) is studied. Two-dimensional nanostructures can be fabricated in geometries that can simulate bulk spin-ice materials and these systems (Artificial spin-ice) have also shown to be home to monopole defects and exotic phase transitions that are driven by the frustration intrinsic to the lattice. However, in order to capture a complete physical model of bulk spin-ice, a 3D geometry is required. This study will fabricate 3D artificial spin-ice structures. Fabrication will be carried out with a novel direct laser writing lithography system that is capable of carving out 3D holes within a resist on the sub-micron scale. These holes can then be filled with a magnetic material such as Nickel. Structures will be made such that they mimic the exact 3D geometry of the magnetic moments on a bulk spin-ice lattice, allowing a direct analogy between the two materials. The magnetic reversal will be studied using a combination of magnetometry and microscopy in order to distinguish phenomena arising from the surface and from the bulk. The work will explore the possibility of creating monopole defects in 3D artificial spin-ice systems, and explore their dynamics in samples of varying defect density.

挫折感是指一个系统内的成对相互作用不能同时得到满足，这种现象对于解释从太阳耀斑的产生到水-冰之间的结合等一系列现象很重要。为了研究挫折感，物理学家寻找可以通过实验直接探测物理元素之间的相互作用的理想系统，如自旋。最近成为密集研究对象的一个这样的凝聚态系统就是自旋-冰材料。这些是块状晶体，其中自旋位于关节四面体的角落上。每个四面体有四个自旋，每个自旋都可以指向四面体的中心或指向四面体的中心。这些自旋想要和它们的邻居们头对着尾地坐在一起，它们感到沮丧，这导致了一种被称为冰规则的最低能量配置，其中两个自旋指向四面体的中心，两个自旋指向。在四面体上翻转一次自转会导致中心有有限磁荷的违反冰规则的缺陷。这些缺陷通过相当于库仑定律的磁相互作用，是矢量场M和H中的磁单极子。自旋冰中单极子的实现是令人兴奋的，并导致了一个新的领域，在那里研究磁荷的运动(磁性)。二维纳米结构可以被制造成可以模拟块状自旋-冰材料的几何形状，并且这些系统(人工自旋-冰)也被证明是由晶格固有的挫折感驱动的单极缺陷和奇异相变的家园。然而，为了捕捉完整的大块自旋冰的物理模型，需要一个3D几何图形。这项研究将制造3D人造自旋-冰结构。制造将使用一种新型的直接激光写入光刻系统进行，该系统能够在亚微米级的抗蚀剂中雕刻出3D孔。然后，可以用镍等磁性材料填充这些孔洞。结构将被制作成模拟块状自旋-冰晶格上磁矩的精确3D几何形状，从而允许在两种材料之间进行直接类比。我们将结合磁学和显微技术来研究磁反转现象，以区分表面和块体产生的现象。这项工作将探索在3D人工自旋-冰系统中产生单极缺陷的可能性，并在不同缺陷密度的样品中探索其动力学。