DMREF: Discovery and Design of Magnetic Alloys by Simulation and Experiment

磁冷却是利用磁场来改变材料的温度，为发电、加热和制冷等应用提供了一种截然不同的能源解决方案。磁冷却是一种潜在的环保、节能技术，其性能优于传统的气体压缩制冷。自发现可以在正常工作条件下将磁性转化为冷却的材料以来，已经有15年多了，但是如何优化这些材料的制造和性能仍然未知。这个设计材料来革新和工程我们的未来（DMREF）项目旨在识别和优化磁性合金的化学成分，并了解控制这一重要行为的基本科学特性。计算和实验设计相结合的方法将用于快速识别最佳候选系统。先进的计算方法将用于预测和设计具有最强效应的合金；发现的最有希望的组合物将被合成并在实验室进行测试。预期的结果是(i)几种用于冷却和制冷的高性能磁性合金的鉴定，以及（ii）对这类极有前途的材料所能达到的性能进行评估。该计划侧重于优化最有前途的一类材料的性能：超磁性Ni-Mn-Sn和Ni-Mn-In-(Co)形状记忆合金。由于两种设计自由度、磁性和晶体结构之间的独特耦合，这些heusler型合金有可能极大地改变我们的冷却和制冷方法。通过量子力学模拟方法和独特的实验能力来测量大磁场下的性能，这一努力将计算/实验方法结合起来进行设计和优化。一组目标性能指标、弹性常数、声子模式、自旋波刚度和交换相互作用能量将使用量子力学模型与现象学描述相结合来计算。对于最有希望的候选材料，将在单晶样品上进行有针对性的实验，通过研究磁场诱导的从马氏体相到奥氏体相的转变，在选定的成分中产生显著的磁化变化，来验证计算模型。最终，该计划将提供一个详尽的评估，在候选的超磁形状记忆合金Ni-Mn-Sn和Ni-Mn-In-(Co)的光谱。

Magnetic cooling, in which a magnetic field is used to change the temperature of a material, offers a profoundly different energy solution to applications involving power generation, heating, and refrigeration. Magnetic cooling is potentially an environmentally friendly, energy-efficient technology capable of outperforming conventional gas-compression refrigeration. It has been over fifteen years since the discovery of materials that can convert magnetism for cooling in normal operating conditions, but much is still unknown about how to optimize the manufacture and performance of these materials. This Designing Materials to Revolutionize and Engineer our Future (DMREF) project seeks to identify and optimize the chemical compositions of magnetic alloys, and understand the fundamental scientific properties that control this important behavior. A combined computational and experimental design approach will be used to identify the optimal candidate systems rapidly. Advanced computational methods will be used to predict and design alloys exhibiting the strongest effect; the most promising compositions discovered will then be synthesized and tested in the laboratory. The expected results are (i) the identification of several high-performance magnetic alloys for cooling and refrigeration, and (ii) an assessment of the performance attainable in this highly promising class of materials.This program focuses on optimizing performance within one of the most promising class of materials: the metamagnetic Ni-Mn-Sn and Ni-Mn-In-(Co) shape memory alloys. Due to a unique coupling between two design degrees of freedom, magnetism and crystal structure, these Heusler-type alloys have the potential to dramatically change our approach to cooling and refrigeration. This effort brings a combined computational/experimental methodology to design and optimization, via quantum mechanical simulation methods and unique experimental capabilities to measure performance under large magnetic fields. A set of target performance metrics, elastic constants, phonon modes, spin wave stiffnesses, and exchange interaction energies - will be calculated using quantum mechanical models coupled with phenomenological descriptions. For the most promising candidates, targeted experiments on single crystal samples will be used to validate the computational models by studying the magnetic field induced transition from the martensite phase to the austenite phase in selected compositions producing a significant change in magnetization. Ultimately this program will provide an exhaustive assessment across a spectrum of candidates in the metamagnetic shape memory alloys Ni-Mn-Sn and Ni-Mn-In-(Co).