Bedingungen für das Auftreten von Ferromagnetismus in realen Gasen

Abstract

We consider a gas consisting of particles (molecules) with spin 1/2 and vanishing electrical charge. We assume the existence of spin-dependent two-body-potentials of interaction between these particles. Our aim is to establish conditions for the appearance of ferromagnetism in such systems. Calculations are done for a modified Lennard-Jones-type two-body-potential. The sum-over states is expanded with respect to cluster-integrals which are approximately calculated up to the fourth order. Cluster of higher order seem to give only uniportant contributions to the conditions mentioned. The conditions for ferrmagnetism are fulfilled, if the density of the gas is higher and the temperature lower than some critical values. The dependence of magnetization on temperature is given and some considerations regarding the equation of state are made. It is supposed that liquids of the same composition and interaction will also show ferromagnetism. The results seem to hold also for potentials which are not of the Lennard-Jones-type, but have the appropriate spin-dependence.