Magnetic Moment Distribution of Nickel Metal

Abstract

The magnetic form factor of nickel has been determined for the first 27 Bragg reflections by the polarized-neutron-beam technique. Fourier inversion of the form factor shows that the moment density is quite asymmetric about the lattice sites and is negative in the region between the lattice sites. The measured form factor agrees well with a free-atom form factor for ${\mathrm{Ni}}^{++}$ provided a uniform negative contribution is included in the moment density. From the comparison of the free-atom and measured form factors it is found that 81 ± 1% of the $3d$ magnetic electrons occupy $T_{2g}$ orbitals, compared with the 60% required for spherical symmetry. The size of the negative contribution needed for agreement between the measured and free-atom form factors agrees well with that given by the Fourier inversion, and the analysis of the data is consistent with the following model for the magnetization of nickel: $3d \mathrm{spin}+0.656\mathrm{}{\mu }_{\beta }$, $3d \mathrm{orbit}+0.055\mathrm{}{\mu }_{\beta }$, negative contribution $-0.105\mathrm{}{\mu }_{\beta }$.