Weise B, Dutta B, Teichert N, Hütten A, Hickel T, Waske A
Leibniz Institute for Solid State and Material Research Dresden, 01069, Dresden, Germany.
Institute for Material Science, TU Dresden, 01062, Dresden, Germany.
Sci Rep. 2018 Jun 14;8(1):9147. doi: 10.1038/s41598-018-27428-8.
Research in functional magnetic materials often employs thin films as model systems for finding new chemical compositions with promising properties. However, the scale-up of thin films towards bulk-like structures is challenging, since the material synthesis conditions are entirely different for thin films and e.g. rapid quenching methods. As one of the consequences, the type and degree of order in thin films and melt-spun ribbons are usually different, leading to different magnetic properties. In this work, using the example of magnetocaloric Ni-Co-Mn-Al melt-spun ribbons and thin films, we show that the excellent functional properties of the films can be reproduced also in ribbons, if an appropriate heat treatment is applied, that installs the right degree of order in the ribbons. We show that some chemical disorder is needed to get a pronounced and sharp martensitic transition. Increasing the order with annealing improves the magnetic properties only up to a point where selected types of disorder survive, which in turn compromise the magnetic properties. These findings allow us to understand the impact of the type and degree of disorder on the functional properties, paving the way for a faster transfer of combinatorial thin film research towards bulk-like materials for magnetic Heusler alloys.
功能磁性材料的研究通常采用薄膜作为模型系统，以寻找具有潜在性能的新化学成分。然而，将薄膜扩大到块状结构具有挑战性，因为薄膜和例如快速淬火方法的材料合成条件完全不同。结果之一是，薄膜和熔纺带中的有序类型和程度通常不同，导致不同的磁性能。在这项工作中，以磁热效应的Ni-Co-Mn-Al熔纺带和薄膜为例，我们表明，如果进行适当的热处理，使熔纺带具有合适的有序程度，那么薄膜的优异功能特性也可以在熔纺带中重现。我们表明，需要一些化学无序才能获得明显且尖锐的马氏体转变。通过退火增加有序度仅在选定类型的无序仍然存在的程度上改善磁性能，而这反过来又会损害磁性能。这些发现使我们能够理解无序类型和程度对功能特性的影响，为将组合薄膜研究更快地转向用于磁性赫斯勒合金的块状材料铺平了道路。
