权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

A Plasmonic Antenna for Magneto-Optical Imaging at the Deep Nanoscale

用于深纳米尺度磁光成像的等离子体天线

基本信息

批准号：
EP/I038470/1
负责人：
Robert Hicken
金额：
$ 79.9万
依托单位：
UNIVERSITY OF EXETER
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FI038470%2F1
关键词：
Plasmonic Antenna Magneto Optical Imaging

项目摘要

Magnetic data storage systems, such as hard disk drives, are constructed from nanoscale magnetic elements. The disk drive industry continually seeks to increase data storage capacity and speed of access. Data is represented in binary format (1s and 0s) by the orientation of a tiny bar magnet (up or down). Today each 'bit' is less than 50 nm long and so the critical features of the read/write transducers must be of comparable size. The time taken to read or write each bit is ~1 ns and becoming shorter. New methods are needed to observe and understand how nanomagnets change their state so that device performance can be improved. Time resolved scanning Kerr microscopy (TRSKM) is the most powerful tool with which to study magnetization dynamics on fs through to ns timescales. A fs laser beam is focused onto and scanned across the surface of the sample in order to construct time resolved magnetic images. The TRSKM in Exeter has internationally leading performance but its spatial resolution is limited to 3/4 of the optical wavelength by the diffraction-limited focused spot size (300 or 600 nm), which is an inherent property of the wave nature of light. We propose to develop a plasmonic antenna that will be placed between the focusing lens and the sample so as to produce a much smaller near-field optical spot and hence greatly increased spatial resolution.Light incident upon a metallic surface forces electrons into oscillation. Plasmonics exploits artificial structure to control the electron motion and, in the present case, to enhance the electric field within a small region of space. For example, one antenna design will be reminiscent of the bulls eye in a dart board. A circular grating structure milled into a thin gold film will capture light and channel energy into a hole at its centre. The hole will resonate like an organ pipe, producing an intense electric field at the end opposite to the grating, close to where the sample will be placed. The sample will modify the resonance of the hole and modify the character of the light reradiated by the grating, which will be detected within the TRSKM. For the antenna to be sensitive to the sample magnetization it must possess an additional novel feature: it must absorb and reradiate light of different polarization with equal efficiency. This will be achieved by introducing an appropriate arrangement of slits into the sides of the hole to control its resonant modes.Focused ion beam milling (FIB) will be used to fabricate antennae and monolithic sample/antenna stacks on planar substrates for optical testing. However, the antenna must be formed on a sharp tip for scanning across the sample surface within the TRSKM. We will fabricate gold tips by depositing gold into a pyramidal-shaped pit in a silicon wafer. FIB milling may be used to define a grating in the gold, before resin is used to fill the remaining volume. The Au and resin will then be peeled off the wafer and FIB milling used to define the hole in the gold at the apex of the pyramid. Finally the tip will be attached to the cantilever arm of an atomic force microscope, which will control the height of the tip above the sample.The tip antenna will be used in two exemplar studies. Time resolved images will be obtained from the pole pieces of a partially-built hard disk writer structure. New information will be obtained about how magnetic flux propagates within the nanoscale constriction at the pole tip. The magnetization dynamics excited in nanoscale magnetic elements by the spin transfer torque effect will also be explored. Electrons carry both charge and spin angular momentum and the injection of electrons with net angular momentum generates a torque that can change the magnetic state of a suitably designed nanoscale element. We will study novel structures that allow optical access to the element and hence provide new information about both the origin and effect of the torque.

磁性数据存储系统，例如硬盘驱动器，由纳米级磁性元件构成。磁盘驱动器行业不断寻求增加数据存储容量和访问速度。数据以二进制格式（1和0）表示，由一个微小的条形磁铁的方向（向上或向下）。如今，每个“位”的长度小于50 nm，因此读/写传感器的关键特征必须具有可比的尺寸。读取或写入每个位所需的时间约为1 ns，并且正在缩短。需要新的方法来观察和理解纳米磁体如何改变它们的状态，从而可以提高器件的性能。时间分辨扫描克尔显微镜（TRSKM）是研究fs到ns时间尺度上磁化动力学的最有力的工具。飞秒激光束聚焦到样品表面上并扫描样品表面，以构建时间分辨的磁图像。埃克塞特的TRSKM具有国际领先的性能，但其空间分辨率受限于衍射极限聚焦光斑尺寸（300或600 nm）的光波长的3/4，这是光的波动性质的固有特性。我们建议开发一种等离子体天线，将其放置在聚焦透镜和样品之间，以便产生更小的近场光斑，从而大大提高空间分辨率。等离子体激元利用人工结构来控制电子运动，并且在本例中，利用人工结构来增强空间小区域内的电场。例如，一个天线设计会让人想起飞镖板上的靶心。一个圆形的光栅结构被研磨成一层薄的金膜，它将捕获光，并将能量引导到中心的一个孔中。孔将像风琴管一样共振，在光栅对面的一端产生强烈的电场，靠近放置样品的地方。样品将改变孔的共振，并改变光栅再辐射的光的特性，这将在TRSKM内被检测到。为了使天线对样品磁化敏感，它必须具有额外的新颖功能：它必须以相同的效率吸收和再辐射不同偏振的光。这将通过在孔的侧面引入适当的狭缝来控制其谐振模式来实现。聚焦离子束铣削（FIB）将用于在平面衬底上制造天线和单片样品/天线堆叠，用于光学测试。然而，天线必须形成在一个尖锐的尖端上，以扫描TRSKM内的样品表面。我们将通过将金沉积到硅晶片上的一个圆形坑中来制造金尖端。在树脂用于填充剩余体积之前，FIB研磨可用于在金中限定光栅。然后将Au和树脂从晶片上剥离，并使用FIB研磨来限定金字塔顶点处的金中的孔。最后，针尖将被连接到原子力显微镜的悬臂上，这将控制针尖在样品上方的高度。针尖天线将用于两个示例性研究。时间分辨图像将从部分构建的硬盘写入器结构的磁极片获得。新的信息将获得有关如何在磁极尖端的纳米级收缩内的磁通量传播。此外，本研究亦将探讨奈米磁性元件之自旋转移矩效应所激发之磁化动力学。电子携带电荷和自旋角动量，并且具有净角动量的电子的注入产生可以改变适当设计的纳米级元件的磁状态的扭矩。我们将研究新的结构，允许光学访问的元素，从而提供新的信息的起源和影响的扭矩。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Time-resolved imaging of magnetic vortex dynamics using holography with extended reference autocorrelation by linear differential operator.

磁性涡流动力学的时间分辨成像，使用线性差分运算符的扩展参考自相关的全息图。

DOI：
10.1038/srep36307
发表时间：
2016-10-31
期刊：
Scientific reports
影响因子：
4.6
作者：
Bukin N;McKeever C;Burgos-Parra E;Keatley PS;Hicken RJ;Ogrin FY;Beutier G;Dupraz M;Popescu H;Jaouen N;Yakhou-Harris F;Cavill SA;van der Laan G
通讯作者：
van der Laan G

Ferromagnetic resonance of patterned chromium dioxide thin films grown by selective area chemical vapour deposition

选择性区域化学气相沉积生长的图案化二氧化铬薄膜的铁磁共振