Size and Ion-Doping Effects on Magnetic, Optical, and Phonon Properties of CuAlO[sub.2] Nanoparticles

The magnetic, optical, and phonon properties of ion-doped CuAlO[sub.2] nanoparticles on the Cu or Al site are theoretically investigated. The room temperature ferromagnetism in CuAlO[sub.2] nanoparticles can be due to the surface, size, and doping effects. The magnetization increases with the decreasing nanoparticle size. The different radii of the transition metal ion and the host Cu ion lead to compressive strain, to the enhancment of the exchange interaction constants, and to increased magnetization M[sub.s] and Curie temperature T[sub.C] . By substitution with Mn or Cr on the Al site, tensile strain, a decrease in M[sub.s] , and an increase in dopants are observed. The size and ion-doping influence on the band-gap energy is also discussed. The phonon energy ω decreases, whereas the phonon damping γ increases with increasing temperature and decreasing NP size. They show a kink around T[sub.C] ∼ 400 K. The behavior of ω and γ for different ion dopings is observed.