Spin Fluctuation Theory in Weak Ferromagnets
The dynamical CPA describes the magnetism from the weak to the strong Coulomb interaction limit. It neglects the nonlocal spin fluctuations, while the self-consistent renormalization (SCR) theory takes into account the non-local spin fluctuations in the weak Coulomb interaction regime. We present in Chap. 5 theoretical framework of the SCR. The SCR is based on the free energy expressed by the dynamical susceptibility. Starting from the RPA susceptibility, we take into account thermal spin fluctuations with use of a sum rule. We elucidate how the Curie–Weiss law in susceptibility occurs in the weak ferromagnets and how much the Curie temperature is reduced by the non-local spin fluctuations in the weak limit.
- 94.M. Cyrot, in Electron Correlation and Magnetism in Narrow-Band Systems, ed. by T. Moriya (Springer, Berlin, 1981) Google Scholar