Spin Density Measurements and the Spin Susceptibility of the 4s Conduction Electrons in Fe

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Abstract
It has been observed that the Mössbauer spectra of many ferromagnetic alloys can be analyzed to give the effect on the internal field at an 57Fe nucleus of a solute atom in any of the first six neighbor shells surrounding an Fe atom. The success of such an analysis indicates that the effects of many elements (e.g., Al, Si, Mn, V, Cr) are quite localized and, in particular, the results of the Al and Si alloys indicate that these atoms can be interpreted as acting like holes in the Fe lattice. From considerations of the various contributions to the hyperfine field in Fe, it appears that for the FeAl and FeSi alloy systems the observed changes can be attributed to changes in the spin polarization of the s conduction electrons as a function of distance from an Fe atom. The main features of the observed variation are: (a) an oscillating polarization whose amplitude of oscillation is much greater than that corresponding to a Ruderman‐Kittel‐Kasuya‐Yosida type calculation and whose sign is such as to show that the indirect exchange interactions in Fe via the 4s conduction band are strongly antiferromagnetic; and (b) the period of the oscillation corresponds to a Fermi radius, kF∼0.95×108 cm−1, which yields a 4s conduction electron/atom ratio of about 0.3. With the assumption of a reasonable magnetic form factor for Fe (that from neutron diffraction measurements), the observed polarization can be Fourier inverted to give the spin susceptibility of the s conduction electrons in Fe. The results of such an inversion yield a spin susceptibility function which has a large peak at the Fermi diameter.