Junichi Kawamura

Fabrication of exchange-coupled α-Fe∕L10-FePd nanocomposite isolated particles

Oriented nanocomposite particles of α-Fe and ordered L10-FePd have been fabricated by electron-beam deposition and successive postdeposition annealing at temperatures higher than 773K. High-resolution transmission electron microscopy, nanobeam electron diffraction, and nanobeam elemental analysis indicated that two regions composed of α-Fe and L10-FePd coexisted in each nanoparticle separated by a diffuse boundary. Magnetic hysteresis measurements using a superconducting quantum interference device magnetometer showed a gradual increase in the saturation magnetization with increasing volume ratio of the α-Fe region, whereas the coercivity decreased with the volume of α-Fe. There were no obvious steps in each magnetization curve. These results indicated the existence of an exchange coupling between the α-Fe and L10-FePd crystallites connected coherently with each other within the nanoparticles. The effects of the α-Fe region size on hard magnetic properties are also discussed.