This project seeks to elucidate materials factors that control the thermodynamic and kinetic stability of the equiatomic compound FeNi with the chemically-ordered tetragonal L10 structure that holds very high potential for rare-earth-free advanced permanent magnet applications. Fundamental exploratory research on magnetic alloys in the near-equiatomic compositional region of the Fe-Ni phase diagram will take place in materials with and without the ternary alloying additions of Ti, V, and Al. These materials will be synthesized in both bulk and thick-film form, with insight gained from film analogs of the focus alloys used to guide rational design of bulk alloys. Correlations between chemical ordering and magnetic properties such as magnetization, anisotropy and Curie temperature will be determined and quantified to facilitate trend prediction.
Astronomers have identified the L10 FeNi phase in selected meteorites and attributed its presence to an extraordinarily slow cooling rate that fosters long-range chemical ordering over a period of 4.6 billion years. Confirmation of the L10 structure in the Fe-Ni system is extremely significant because the tetragonal distortion that accompanies the chemical ordering in this structure gives rise to appreciable anisotropy. The development of rare-earth-free permanent magnet materials is essential to offset supply limitations and ensure U.S. competitiveness. Attainment of a rare-earth-free magnetic material with very high magnetocrystalline anisotropy would carry tremendous impact that ranges from the basic science realm all the way to advanced applications of great societal importance. Students supported by this grant will obtain an interdisciplinary research experience via educational exchange at three geographically diverse, strong science and engineering schools.