FePt nanoparticles with thermally stable room-temperature ferromagnetism are investigated. The monodisperse nanoparticles are prepared by chemical synthesis and a salt-matrix annealing technique. Structural and magnetic characterizations confirm the phase transition from the disordered face-centered cubic structure. In this paper, 3 nm FePt nanoparticles are first synthesized by superhydride re...

The Mott-Anderson transition has been known as a metal-insulator (MI) transition due to both strong electron-electron interaction and randomness of the electrons. For example, the MI transition in doped semiconductors and transition metal oxides has been investigated up to now as a typical example of the Mott-Anderson transition for changing electron correlations by carrier number control in co...

A theory of transition free-electron laser ~FEL! driven by an electron bunch of finite longitudinal length is presented. It is shown that one can introduce concepts of a long, a short, and a very short bunch depending on the degree of correlation between the bunch effective length and the transition radiation formation length. It is obtained that a long Gaussian bunch produces an electromagneti...

Electron-electron interactions are the fastest processes in materials, occurring on femtosecond to attosecond timescales, depending on the electronic band structure of the material and the excitation energy. Such interactions can play a dominant role in light-induced processes such as nano-enhanced plasmonics and catalysis, light harvesting, or phase transitions. However, to date it has not bee...

To understand the essence of the exciton Mott transition in three-dimensional electron-hole systems, the metalinsulator transition is studied for a two-band Hubbard model in infinite dimensions with interactions of electronelectron (hole-hole) repulsion U and electron-hole attraction −U . By using the dynamical mean-field theory, the phase diagram in the U -U ′ plane is obtained (which is exact...

FePt nanoparticles with thermally stable room-temperature ferromagnetism are investigated. The monodisperse nanoparticles are prepared by chemical synthesis and a salt-matrix annealing technique. Structural and magnetic characterizations confirm the phase transition from the disordered face-centered cubic structure. In this paper, 3 nm FePt nanoparticles are first synthesized by superhydride re...