High-anisotropy nanoparticles of a size below 10 nm with a high degree of atomic ordering are needed as building blocks for applications in areas such as permanent magnetism, magnetic recording, and biomedicine. For this reason, nanoparticles of a variety of materials ranging from transition metals to dilute magnetic semiconductors have been explored. Rare-earth transition-metal (RE-TM) alloys show superior permanent-magnet magnetic properties in the bulk, but the synthesis and application of RE-TM nanoparticles has remained a challenge due to the requirement of a high temperature annealing at above 900°C for alloy formation and subsequent crystalline ordering. Researchers at the University of Nebraska MRSEC and their colleagues at the University of Delaware have developed a single-step method to produce highly ordered and single-phase RE-TM nanoparticles such as YCo5 and Y2Co17, by employing a cluster-deposition system without high-temperature thermal annealing. [Nano Letters (2011)] This research provides the basis for significant development of RE-TM nanoparticles for important new applications.
High-resolution transmission-electron-microscopy image of 8 nm YCo5 nanoparticle (left) and hexagonal CaCu5 crystal structure (right).