THE MAGNETIC-PROPERTIES OF A UNIFORM-SIZE FINE-PARTICLE FERROFLUID IN THE DIMER MODEL IN 3 DIMENSIONS

Using a statistical mechanical method we have calculated the magnetization and the initial susceptibility for a ferrofluid composed of fine, uniform spherical particles, taking into account the magnetic dipole interactions in the dimer model under a reasonable condition. We have found that the initial susceptibility is consistent with a Curie law rather than a Curie-Weiss law. That means, for low fields and relatively high temperatures, the system of N particles, in the dimer model, behaves as a superparamagnetic gas of N/2 pairs.