Novel rare-earth free magnetic nanostructures*

Magnetic nanostructuring including stabilization of novel structures without critical elements, easy-axis alignment, and self-assembly are important for creating new magnetic materials. We use a single-step process in a cluster-deposition system to fabricate rare-earth-free nanostructured magnetic materials with potential for high-energy magnet or spintronics applications.\footnote{B. Balamurugan, B. Das, D. J Sellmyer et al., \textit{Advanced Materials}, \textbf{25}, 6090 (2013).} For example, Mn$_{5}$Si$_{3}$ nanoclusters of diameter about 8 nm form hexagonal D8$_{8}$ structure and show strong ferromagnetic properties with a high $T_{c} =$ 590 K, an appreciable $K_{1} =$ 11 Mergs/cm$^{3}$, and a high $J_{s} = $12.5 kG. This result is in a sharp contrast to the antiferromagnetic ordering observed in bulk Mn$_{5}$Si$_{3}$ with $T_{N} =$ 100 K, and is supported by DFT calculations. On the other hand, MnSi nanoclusters form B20-type cubic crystal structure and are ferromagnetic below T $=$ 25 K. Skyrmion-type spin structures have been observed in MnSi thin films and evidence for such structures in nanoclusters will be discussed.