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A possibility of half-metallic ferromagnetism for the homogeneous phase in the half-Heusler alloy-based DMS CoTi1− xFe xSb is predicted. A phase diagram of the spinodal and binodal decomposition is constructed through the evaluation of the mixing free energies. By applying the Monte Carlo simulation method to the Ising model with realistic chemical pair interactions between Fe magnetic impurities, we simulate the spinodal decomposition and nanoscale separation in this alloy. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of XYSi (X = Ni, Pd, Pt; Y = Mn and Cr) are investigated through the ab initio calculation of the electronic structure, equilibrium lattice constant, magnetic exchange interaction and Curie temperature. The role of X and Y elements in the opening of the minority spin gap is discussed. The Fermi level lies closer to the conduction band for slighter X or Y. XYSi is half-metallic ferromagnets at equilibrium lattice constant, except PdMnSi. The Curie temperature of 1076, 785 and 634 K has been predicted by Monte Carlo simulations for NiMnSi, PtMnSi and NiCrSi, respectively. [ABSTRACT FROM AUTHOR]

We present a first principle study of the half-metallicity and ferromagnetism in half-heusler alloys XYSi (X = Ni, Pd and Pt; Y = Cr and Mn). The equilibrium lattice constants are predicted by means of the ultrasoft pseudo-potential method. The electronic structure and magnetic exchange interaction of various alloys are investigated within KKR-LSDA. The Curie temperature is predicted by using the Monte Carlo simulation, the random phase and mean field approximations, as well. The role of elements X, Y components and influence of the lattice parameters in stabilizing half-metallicity and ferromagnetism are discussed. Except PdMnSi, alloys are half-metallic at equilibrium lattice constant. The Curie temperatures of 634 K, 785 K, and 1076 K for NiCrSi, PtMnSi and NiMnSi, respectively, are predicted by Monte Carlo simulation. The structural stability of C1b is also considered. [ABSTRACT FROM AUTHOR]

We propose new-type ferromagnetic semiconductors based on CaO and K2S without any transition metal elements. These materials show transparent and half-metallic ferromagnetism if the deep-impurity-band width ( W) induced by doping of C, N, Si, or Ge impurities, and the electron-correlation energy ( U) satisfy the Stoner’s condition of highly correlated electron system ( U> W). Based on our first-principles calculations, we demonstrate that these materials satisfy the Stoner’s condition, and could be new candidates for transparent and half-metallic DMSs. [ABSTRACT FROM AUTHOR]

Abstract: Based on ab initio electronic structure calculations by self-interaction-corrected local-density-approximation (SIC-LDA) with the Korringa–Kohn–Rostoker coherent potential approximation (KKR-CPA), we propose a materials design for high efficiency photovoltaic solar cells (PVSCs). It is shown that (i) the concentration dependence of the mixing energy of CuIn1−xGaxSe2 shows upward convexity, thus this system favors phase separation. Due to the type II band alignment between CuInSe2 and CuGaSe2, efficient electron–hole separation is realized in decomposed phase of this system. (ii) CuIn1−xZn0.5xSn0.5xSe2 has a direct band gap and no impurity state appears in the gap. Therefore, cost reduction is possible by using Zn and Sn instead of In. (iii) n-type CuAl1−xSnxS2 and p-type Cu1−xVCuxAlS2 have negative activation energy for doped impurities and are expected to be low-resistive transparent conducting sulfides, which should be useful for CuInSe2-based PVSCs. [Copyright &y& Elsevier]