Concentration dependence of the wave vector of the spin-density wave of chromium alloys

Abstract

The static, unenhanced paramagnetic susceptibility of pure Cr and its dilute alloys with V and Mn is computed within the random-phase approximation at zero temperature. Matrix elements are calculated using a linear-combination-of-atomic orbitals scheme and alloying is treated by both the rigid-band and coherent-potential approximations. The susceptibility exhibits peaks at wave vectors which correlate well with Fermi-surface nesting features and which are indicative of antiferromagnetic instabilities leading to spin-density-wave ground states. These wave vectors agree to within 1% with neutron scattering measurements of the spin-density-wave wave vector in pure Cr, and the calculated dependence of this wave vector on V or Mn impurity concentration follows experimental variations closely. The unenhanced paramagnetic susceptibility of pure Mo is computed as well; and the absence of a spin-density wave, despite strong similarities between the Fermi surfaces of Cr and Mo, is attributed to matrix-element behavior and exchange and correlation corrections.