MICROSCOPY Vol.47▶No.3 2012
■Researches Today

Atomic Structure Imaging of Ferromagnetic Long-Range Ordered Alloy Nanoparticles

Kazuhisa Sato, Toyohiko J. Konno and Yoshihiko Hirotsu

Abstract: We have studied the atomic ordering and structures of hard magnetic L10–type FePd and CoPt alloy nanoparticles using aberration-corrected high-resolution transmission electron microscopy (HRTEM). The key issue throughout this study is the atomic ordering in the alloy nanoparticles; in view of excellent hard magnetic properties due to the high magnetocrystalline anisotropy energy, which is dependent on the long-range order parameter. The kinetics of atomic ordering plays a crucial role here, i.e., annealing below a reduced order-disorder transformation temperature is essential in obtaining the L10 ordered phase in small nanoparticles. Imaging using aberration-corrected HRTEM unambiguously revealed the atomic structures of the alloy nanoparticles 2−10 nm in diameter. The technique developed rapidly in the past ten years and is now practically available for the structural analysis in materials science.

Key words: High-resolution transmission electron microscopy, aberration correction, magnetic alloy nanoparticles, long-range order, size effect