Electronic and magnetic properties of spiral spin-density-wave states in transition-metal chains

The electronic and magnetic properties of one-dimensional (1D) 3d transition-metal nanowires are investigated in the framework of density functional theory. The relative stability of collinear and noncollinear (NC) ground-state magnetic orders in V, Mn, and Fe monoatomic chains is quantified by computing the frozen-magnon dispersion relation [Delta]E(q)as a function of the spin-density-wave vector q. The dependence on the local environment of the atoms is analyzed by varying systematically the lattice parameter a of the chains. Electron correlation effects are explored by comparing local spin-density and generalized-gradient approximations to the exchange and correlation functional. Results are given for [Delta]E(q), the local magnetic moments [mu] sub(i) at atom i, the magnetization-vector density m(r), and the local electronic density of states [rho] sub(i[sigma])([epsilon]). The frozen-magnon dispersion relations are analyzed from a local perspective. Effective exchange interactions J sub(ij) between the local magnetic moments [mu] sub(i) and [mu] sub(j) are derived by fitting the ab initio[Delta]E(q) to a classical 1D Heisenberg model. The dominant competing interactions J sub(ij) at the origin of the NC magnetic order are identified. The interplay between the various J sub(ij) is revealed as a function of a in the framework of the corresponding magnetic phase diagrams.