Single-site theory of finite-temperature magnetism in amorphous and liquid alloys

A simple theory of finite-temperature magnetism for amorphous and liquid alloys which interpolates between the weak and strong Coulomb-interaction limits within a single-site approximation is presented on the basis of the functional integral technique. The theory is applied to liquid Fe and Ni. It is shown that the line broadening in the density of states due to thermal spin fluctuation is comparable to that due to the structural disorder; thus the thermal spin fluctuations are indispensable for understanding the experimental data of liquid transition metals and alloys. Calculated ratios of the Curie constant in liquid to the Curie constant in a solid explain well the experimental data, while the jumps of inverse susceptibility ${\chi }^{\mathrm{-}1}$ at the melting point are shown to be sensitive to the structural models and parameters. The present theory yields the packing fractions in the hard-sphere model larger than those estimated by the previous theories without thermal spin fluctuations.