The paramagnetic state of itinerant electron systems with local magnetic moments. I. Static properties

Abstract

A model previously used for treating thermodynamic properties is developed further to discuss the wave-vector-dependent susceptibility chi (q) and the associated static correlation functions. A consistent theory is given of the temperature dependence of the uniform susceptibility and of the wave-vector and temperature dependence of paramagnetic diffuse neutron scattering. The theory is applied quantitatively to CeFe2, Fe and MnSi above their magnetic ordering temperatures and to FeSi at high temperatures. In CeFe2 and MnSi the enhancement of the Curie constant and the forward scattering peak in the neutron data are both attributed to long-wavelength 'longitudinal' fluctuations of the magnetic moment superposed on strong transverse spin disorder. The situation is predicted to be similar in BCC Fe and this differs sharply from the strong short-range order picture of Prange and Korenman (1978), Capellmann (1979) and Sokoloff (1975).