Processing of magnetic materials enhanced by electric fields or currents

本项目第二阶段的延续方案旨在将我们第一阶段的成果和经验扩展到二元硬磁合金电流加工的结论性图景。我们的关键问题是：从观察到的原子扩散和相变现象到电场或电流影响下的原子级迁移过程的本质联系是什么？为了回答这个问题，显微组织和合金成分对扩散和转变的影响将通过实验和模拟来探索，将原子的迁移和相的化学顺序联系起来。我们将重点关注这些问题，以进一步发展对电迁移和相有序的理解。在这篇文章中，我们将使用不同的二元材料系统，将实验和理论工作定位于一个共同的尺寸尺度。这将从两个方面来完成：通过使用先进的处理和表征技术，以及采用基于原子点缺陷形成和迁移数据的确定性宏观扩散模型。通过这种结合，我们有信心将目前所选的无稀土材料体系的退火实验与原子尺度的有序机制联系起来。通过对合金的系统研究，我们将描述化合物和元素性质对电流诱导形成硬磁相的影响。这项工作计划依赖于两个小组共同努力的思想和成果的协同作用。在项目的实验方面，我们将扩展和完善第一期开发的四种拟议材料系统（Mn-Al, Mn-Ga， Fe-Pt和Fe-Ni）的工艺和设置。通过这种方法，我们打算确定驱动因素并获得电流辅助处理这些磁性材料的定量数据。此外，计划进一步研究微结构特征（缺陷结构、错配或取向偏差）对观察到的电流驱动的原子扩散和相形成的影响。理论任务将以所选模型系统的实验活动为指导。相变和扩散对实验的定量数据将与原子模拟结果构建的扩散模型的特征进行比较。该模型的一个重要特征将是扩散（通过温度）和漂移（通过电场或电流）的区分，解决了将焦耳加热与电迁移分离的问题。晶体和界面取向与电场或电流相关的理论结果将补充界面、层状前驱体和晶粒取向分辨电流退火的实验结果。

This continuation proposal for period two of this SPP aims to extend our results and experiences from period one to a conclusive picture of electric current processing of binary hard magnetic alloys. Our key question is: what is the essential link from the observed atomic diffusion and phase transition phenomena to the atomic level migration processes under the influence of an electric field or current? To answer this question, the influence of microstructure and alloy composition on diffusion and transformation will be explored by experiments and simulations, linking migration of atoms and chemical ordering of phases. We will focus on these issues to further develop the understanding of electromigration and phase ordering. For this continuation, we will orient experimental and theoretical work to a common size scale using different binary material systems. This will be done from both sides: by using advanced processing and characterization techniques and by employing a deterministic, macro-scale diffusion model based on atomistic point-defect formation and migration data. Through this combination, we are confident to connect the current annealing experiments on the chosen rare-earth-free material systems to atomic scale ordering mechanisms. By a systematic study of the alloys, we will describe influences of compound and element properties on the current induced formation of the hard magnetic phases. This work plan relies on the synergy of ideas and results of the joint efforts of the two groups.On the experimental side of the project, we will expand and refine the processes and setups developed the first period to the four proposed material systems (Mn-Al, Mn-Ga, Fe-Pt and Fe-Ni). With this approach, we intend to identify the driving forces and obtain quantitative data on the electric current assisted processing of these magnetic materials. Moreover, intensified investigations of the effects caused by microstructural features (defect structures, misfits or misorientations) in the observed current driven atomic diffusion and phase formation are planned.The theoretical tasks will be guided by the experimental activities on the chosen model systems. Quantitative data from phase transition and diffusion pair experiments will be compared with features of diffusion models constructed from atomistic simulation results. An important feature of the models will be the discrimination of diffusion (by temperature) and drift (by electric field or current), addressing the problem of separating Joule heating from electromigration. Theoretical results on crystal and interface orientations relative to the electric field or current will complement experimental results on interfaces, layered precursors and grain-orientation resolved current annealing.