Distribution of magnetic moment inNi3Al

The unpaired-spin density distribution in the weakly ferromagnetic ordered alloy ${\mathrm{Ni}}_3$Al was determined by polarized-neutron diffraction measurements on a single-crystal sample of 75.9-at.% Ni. In this ${\mathrm{Cu}}_3$Au-type structure, the local magnetization at a Ni site is similar in its radial dependence and cubic components ($84\%T_{2g},16\%E_g$) to that in pure nickel, though it is much smaller in magnitude. (The magnetic moments of the excess Ni atoms in Al sites are not significantly different from those at the Ni sites.) Consistent with the tetragonal environment of each Ni site, the magnetization distribution is further lowered in symmetry, resulting in an extreme situation in which the uncompensated spin is located predominantly in the lobes directed toward Ni neighbors and hardly at all in those directed toward Al neighbors. Comparison is made with the components of the Fermi-level density of states derived from a band calculation by Fletcher; the neutron-diffraction results are found to be qualitatively in accord.