We study paramagnetic characteristics of ferromagnetic metals near the Curie temperature TC using the dynamic spin fluctuation theory. In contrast with most first-principles calculations, our results for the uniform paramagnetic susceptibility show a clear deviation from the Curie-Weiss law. We demonstrate that the susceptibility and correlation radius have the power-law behavior at temperatures up to 1.1-1.15 TC, which gives an estimate for the region of critical temperatures in metals. Our theoretical critical exponents for Fe, Co, and Ni are in reasonable agreement with the low-field susceptibility measurements and neutron scattering experiments.

We study the dependence of magnetic properties: Curie temperature, mean and local magnetic moments—on the type of crystal lattice and average number of d electrons per atom. The problem is considered in two approximations: with spin fluctuations not taken into account, in the Stoner mean field theory, and with spin fluctuations taken into account, in the dynamic spin fluctuation theory (DSFT). In the DSFT, we obtain an analogue of the Slater–Pauling curve for the mean magnetic moment at finite temperatures. Numerical results in the DSFT are in qualitative agreement with experiment: with magnetic phase diagram and dependence of magnetic moment on concentration in ferromagnetic alloys.

Paramagnetic susceptibility and spin-density correlation function near the Curie temperature T C are studied using the dynamic spin fluctuation theory. The calculated critical indices of the susceptibility and correlation radius for Fe, Co, and Ni are found in reasonable agreement with bulk susceptibility measurements and neutron scattering experiments. It is shown that the critical power-law behavior holds at temperatures up to 1.10–1.15 T C , which gives an estimate of the critical temperature region in ferromagnetic metals.