On the Form of the Functional Dependence of the Magnetic Susceptibility of a Magnetic Liquid on the Temperature

Abstract

The fulfilment of the Curie and Curie–Weiss laws for a magnetic dispersive nanosystem is critically discussed. Results of investigations into the temperature dependences of the magnetic susceptibility of these media are presented for a wide range of dispersive phase concentrations. Based on the results of these investigations, the validity of these laws for the χ/μ and χ^–1 is checked. A conclusion is drawn that the Curie law is valid only for colloids with a certain limited range of magnetic nanoparticle concentrations due to difference in magnitudes of the external magnetic field and the field acting on an individual nanoparticle (effective field). The effective field parameter is calculated in the context of the effective field theory. It is indicated that the value of the effective field parameter is not a constant and depends on the concentration of magnetic nanoparticles and on the temperature of the disperse medium as a whole.