Magnetic Moments and Unpaired Spin Densities in the Fe-Rh Alloys

The distribution of magnetic moments in the Fe-Rh system has been investigated by the neutron diffraction technique in the composition range between 35 and 50 at.%Rh. These alloys have chemical order of CsCl type; the body-corner positions are occupied by FeI atoms and the body centers by Rh and FeII atoms. The magnetic moments in ferromagnetic alloys containing 35, 40, and 48% Rh are ${\mu }_{\mathrm{FeI}}=3.1\mathrm{}$ ${\mathrm{\mu }}_{\mathit{B}}$, ${\mu }_{\mathrm{FeII}}=2.5\mathrm{}$ ${\mathrm{\mu }}_{\mathit{B}}$, and ${\mu }_{\mathrm{Rh}}=1.0\mathrm{}$ ${\mathrm{\mu }}_{\mathit{B}}$ at 25°C. The moment of the FeI atom in the 50% Rh alloy, which is antiferromagnetic at room temperature, increases to 3.3 ${\mathrm{\mu }}_{\mathit{B}}$. A detailed study of the unpaired spin density distribution in the 48% Rh alloy was made by the polarized beam technique. While the FeI atom has a nearly spherical density distribution, that of the Rh atom shows a strong tendency towards $e_g$ symmetry. The coherent nuclear scattering amplitude of Rh was determined to be 0.585±0.005×${10}^{-12\mathrm{}}$ cm.