Magnetic form factor and spin-density asphericity of Ni-Cu.

Abstract

Magnetic form-factor measurements were made on single crystals of a Ni-Cu alloy containing 47.6 at.% Cu. The results give a magnetic moment of 0.088 ${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$/atom at $T=4.2$ K and $H=40$ kOe in excellent agreement with bulk magnetization data. Despite this order of magnitude decrease in moment relative to Ni, the form factor is the same in both the radial distribution and the asphericity as that previously observed for pure Ni. This result is in strong contrast with an early coherent potential approximation calculation which yields a continuous variation of $\ensuremath{\gamma}$, the fractional ${E}_{g}$ population, with Cu content. It is suggested that some of this discrepancy may be attributed to the neglect of local environment effects, which are known to be importnat for the magnetism of Ni-Cu alloys.