Nanoscale Sculpting of Ferromagnetic Surfaces with Magnetic Configurational Forces

在这项工作中，研究人员提出了一种在铁磁表面上的新的“磁场诱导的构型力”，以及利用它在纳米到微观尺度上完成任何所需顺序和尺寸分布模式的“引导组装”的方法。他们展示了他们的初步实验结果，以证明他们的“磁场诱导表面扩散”想法的可行性，并请求资助进一步探索这一新现象，以更好地控制这一过程，获得基本的理解，并将其发展成为一种新的铁磁表面纳米制造技术。除了实验调查外，拟议的研究还包括开发一个分析框架来描述动力学和对该现象的定量描述。在过去的十年中，纳米结构的受控和有序模式的制造一直是一些研究工作的焦点。这种努力的一个例子是半导体薄膜中的应变诱导自组装，它利用弹性构形力，这种弹性构形力是弹性能和表面能之间在最小化系统自由能方面的竞争的结果。在纳米级组装和制造的背景下，一个相关的问题是，是否有其他种类的纳米级结构力作用于固体表面，可以利用这些力来驱动有序和受控的结构生长。在铁磁表面的情况下，本提案(i)证明了磁性构形力的存在，并提供了支持的初步实验证据，（ii）试图在系统的实验计划中进一步探索它。这种构型/驱动力是磁场能量和表面能量竞争的结果。在有利条件下，磁构形力可以通过表面扩散诱导表面形状的演变。这一建议的智力价值在于探索了利用磁场驱动铁磁材料表面扩散的新概念。这一概念以前从未被讨论或报道过。基于这一新思路，该提案还旨在开发一种新的纳米制造工具，以实现具有任何所需空间位置和尺寸分布的纳米结构模式的“引导组装”。提出的研究还旨在通过引入磁弹性化学势的概念来发展对这一现象的分析描述。该研究将基于首席研究员和他的合作者之间的跨学科协作，他们各自具有应用力学和材料科学的背景。拟议研究的更广泛影响在于(i)广泛有效地传播通过本研究获得的见解，（ii）培训研究生作为其博士课程的一部分，（iii）为历史上的黑人学院或大学（HBCU）的本科生提供研究和教育机会，以及（iv）与布朗大学的NSF支持的MRSEC计划进行互动，将该研究项目纳入教师研究经验（RET）推广计划。参与该项目的研究生和本科生将有机会参加研究会议，展示他们的工作并获得宝贵的职业经验。

Nanoscale Sculpting of Ferromagnetic Surfaces with Magnetic Configurational ForcesNSF 0510030PI - Guduru, Brown UniversityIn this work, the investigators propose a new "magnetic field induced configurational force" on ferromagnetic surfaces and ways to exploit it to accomplish "guided assembly" of patterns of any desired order and size distribution at nano to micro scale. They present results of their preliminary experiments to demonstrate the feasibility of their idea of "magnetic field induced surface diffusion" and request funding to explore this new phenomenon further to achieve better control over the process, gain a fundamental understanding and also develop it into a novel nano-manufacturing technique for ferromagnetic surfaces. In addition to the experimental investigation, the proposed research includes development of an analytical framework to describe the kinetics and a quantitative description of the phenomenon. Fabrication of controlled and ordered patterns of nanostructures of technological interest has been the focus of several research efforts during the past decade. An example of such efforts is the strain induced self-assembly in semiconductor thin films that exploits an elastic configurational force that arises as a consequence of the competition between elastic energy and surface energy in minimizing the system free energy. A relevant question in this context of nanoscale assembly and fabrication is whether there are other kinds of configurational forces at nanoscale that act on solid surfaces, which can be exploited to drive ordered and controlled structure growth. In case of ferromagnetic surfaces, this proposal (i) demonstrates the existence of a magnetic configurational force and presents supporting preliminary experimental evidence and (ii) seeks to explore it further in a systematic experimental program. This configurational/driving force results from the competition between magnetic field energy and surface energy. Under favorable conditions, the magnetic configurational force can induce surface shape evolution through surface diffusion. The intellectual merit of this proposal lies in exploring a new concept of driving surface diffusion in ferromagnetic materials using magnetic field. This concept has not been discussed or reported before. Based on this new idea, the proposal also aims to develop a new nanofabrication tool to accomplish "guided assembly" of patterns of nanostructures with any desired spatial location and size distribution. The proposed research also aims to develop an analytical description of the phenomenon by introducing the concept of magneto-elastic chemical potential. The research will be based on a synergistic interdisciplinary collaboration between the principal investigator and his collaborator, with respective backgrounds in Applied Mechanics and Materials Science. The broader impact of the proposed research lies in (i) wide and effective dissemination of the insights gained through this research, (ii) training a graduate student as part of his/her Ph.D. program, (iii) providing research and educational opportunities to undergraduate students from a Historically Black College or University (HBCU) and (iv) interacting with Brown's NSF supported MRSEC program to include this research project in the Research Experience for Teachers (RET) outreach program. The graduate and undergraduate students working on this project will be provided opportunities to participate in research conferences to present their work and gain valuable career experience.