Magnetization Distribution in a Palladium-Rich FePd Alloy

A ferromagnetic ${\mathrm{Fe}}_{0.013}$ ${\mathrm{Pd}}_{0.987}$ single crystal was examined with the polarized-beam neutron-diffraction technique in a study of the distribution of the localized magnetization in the alloy. Intensities of all nineteen Bragg reflections out to $\frac{sin\theta }{\lambda }=0.90\mathrm{}$ ${\mathrm{\AA }}^{-1\mathrm{}}$ were measured at 4.2°K in a field of 14 kOe, yielding the magnetic form factor averaged over all atoms. These data are fitted to a linear combination of calculated $3d$ and $4d$ free-atom form factors, resulting in a moment of $0.050\pm 0.006 {\mu }_B$ of $3d$-like moment and $0.088\pm 0.008 {\mu }_B$ of $4d$-like moment per average atom. A Fourier inversion of the magnetic scattering amplitudes emphasizes the aspherical shape of the unpaired-electron distribution. The over-all $\frac{E_g}{T_{2g}}$ ratio is 0.39±0.02. The measured saturation magnetization of this alloy is $0.114\pm 0.004 {\mu }_B$ per atom at 4.2°K, which is considerably smaller than the total moment of $0.138 {\mu }_B$ seen by neutron diffraction. This discrepancy suggests a negative conduction-electron polarization of $-0.024\mathrm{}\pm 0.011 {\mu }_B$ per atom. The temperature dependence of the magnetic scattering amplitude and the saturation magnetization indicate that the conduction-electron polarization disappears near the Curie temperature, which is about 55°K. In addition, these data suggest that the $3d$ moment on an Fe atom and the $4d$ moments on surrounding Pd atoms are strongly coupled, although the range of the Pd polarization is not determined. The total $d$ moment associated with the moment cluster around each impurity site is $10.7\pm 0.6 {\mu }_B$.