Dynamical effect of spin fluctuations in itinerant electron magnetism

The authors present a method which takes account of the quantum effect of spin fluctuations on itinerant electron ferromagnets in the functional integral formalism and in the gaussian approximation. Using a similar approximation to that introduced by Hertz and Klenin (1977) and the results obtained in the authors' previous work they obtain the dynamical spin susceptibility. Dynamics of spin fluctuations are taken into account through the amplitudes of the local spin fluctuations which are the most fundamental parameters dominating the thermodynamical and magnetic properties of the system. It is shown by simple numerical examples that a remarkable improvement is established for the temperature dependence of the spontaneous magnetisation and the paramagnetic susceptibility as compared with the results obtained in the so-called static approximation.