Processing of magnetic materials enhanced by electric fields or currents

这个SPP的第二阶段的延续建议旨在将我们的结果和经验从第一阶段扩展到二元硬磁合金的电流处理的结论性图片。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，微观结构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有序化联系起来。我们将专注于这些问题，以进一步发展电迁移和相序的理解。为了继续，我们将使用不同的二元材料系统将实验和理论工作定位到一个共同的尺寸尺度。这将从两个方面：通过使用先进的处理和表征技术，并通过采用确定性的，宏观尺度的扩散模型的基础上原子点缺陷的形成和迁移数据。通过这种结合，我们有信心将当前对所选无稀土材料系统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。该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，我们将把第一阶段开发的工艺和设置扩展和完善到四种拟议的材料体系（Mn-Al、Mn-Ga、Fe-Pt和Fe-Ni）。通过这种方法，我们打算确定的驱动力，并获得这些磁性材料的电流辅助处理的定量数据。此外，在所观察到的电流驱动的原子扩散和相形成的微观结构特征（缺陷结构，失配或取向差）所造成的影响的加强调查planned. Theoretical任务将由选定的模型系统上的实验活动的指导。从相变和扩散对实验的定量数据将比较原子模拟结果构造的扩散模型的功能。该模型的一个重要特征是区分扩散（通过温度）和漂移（通过电场或电流），解决焦耳加热与电迁移分离的问题。晶体和界面取向相对于电场或电流的理论结果将补充实验结果的接口，分层前体和晶粒取向解决电流退火。

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.