Novel Nanostructures for High-Energy Nanocomposite Permanent Magnets

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TECHNICAL: Magnetic interactions between hard and soft magnetic phases in nanostructured two-phase composites result in permanent magnet materials with significantly enhanced magnetic properties. The properties dramatically increase with increasing soft magnetic phase fraction. However, in granular materials the soft magnetic phase fraction is limited to about 15 percent by the development of soft magnetic grain/soft magnetic grain neighbors. However, the development of novel nanostructures via eutectic phase transformations offers the potential to increase the volume fraction of the soft magnetic phase to 20-30 percent. The objective of this project is to develop microstructural selection maps for ternary Sm-Co-T alloys in the vicinity of the binary Sm-Co eutectic at 8 atomic percent Sm. With this information, alloys can be designed with high Co content with eutectic structures that avoid formation of primary Co. The microstructural selection maps will be determined for both conventionally processed alloys and after rapid solidification. Rapid solidification processing effectively refines the scale of the soft magnetic phase to the nanostructural level necessary for effective exchange interactions between the hard and soft magnetic phases. The magnetic properties of the nanocomposite permanent magnets will be determined from hysteresis loops as a function of temperature in order to understand the behavior of nanocomposite permanent magnets as a function of temperature. DC demagnetization and isothermal remanence magnetization measurements will provide additional insight into the magnetic behavior, especially the reversal processes and interphase magnetic interactions. The magnetic behavior of the nanocomposites will be closely tied to the nanostructures by characterizing structures using x-ray diffraction and scanning and transmission electron microscopy. Three-dimensional atom probe tomography and three-dimensional field ion microscopy will also be used to characterize the nanostructures; this will be accomplished in collaboration with Dr. Frederic Danoix of the University of Rouen in France. NON-TECHNICAL: Rare earth permanent magnets are integral to technological advancements. As a result, continued development of improved permanent magnets directly benefit society by providing advanced electronic devices, new medical imaging capabilities, and countless other applications, some known and some not yet imagined. Additionally, the research will provide fundamental understanding of solidification of ternary alloys at and near eutectic compositions. This project will also educate and train the next generation of scientists and industry leaders, primarily through the integration of teaching and research by involving undergraduate and graduate students in research. Collaborative research with researchers at the University of Rouen is planned, with graduate students involved with short-term visits to the University of Rouen to conduct the research experiments. Collaborations with researchers at National Laboratories and use of national user facilities will also expand the experiences of students involved in this project. The PI has also developed a course in nanomaterials, and discoveries made in this project will be incorporated into it.