One of the grand challenges in nanomagnetism is that of significantly increasing the energy product of permanent-magnet materials. Applications of these materials are ubiquitous in transportation, energy and information systems, and advances in this field would have important implications in energy conservation and related technologies. In recent years the concept of mixing high magnetization and high coercivity magnetic phases with nanoscale dimensions has been advanced to improve the energy density of permanent magnets. However, up to now the experimentally achieved energy products have been limited because of difficulties in fabricating the composite materials with uniform nanostructuring at a 10 nm length scale. Recent work in collaboration with scientists at the International Center for Materials Physics, Chinese Academy of Sciences, Shenyang, has shown that multilayering a high-coercivity material based on Nd2Fe14B (NFB) with Fe can lead to ideal magnetic coupling. The figure below shows the as-deposited multilayer structure with 16 nm of NFB (grey) and 6 nm of Fe (black/white). After heat treatment a fine scale two-phase nanocomposite granular structure is formed with excellent properties.
This research is supported by the National Science Foundation, Division of Materials Research, Materials Research Science and Engineering Program, Grant 0213808.
D. Sellmyer, R. Skomski, W. Liu (CAS), Handbook of Advanced Magnetic Materials, Springer, 2006