The magnetic susceptibility of the compounds (4-Cl-C6H4NH3)2FepZn1-pCl4 has been studied according to the change in the magnetic ion concentration (p = 0.1, 0.2, 0.4, 0.6, 0.75, 0.9 and 1.0). The size of the domain was found to vanish at the critical concentration 0.1 mol fraction. For the parent compound, p = 1.0, the investigated magnetic susceptibility showed antiferromagnetic character. Dielectric constant behaviour could be explained on the bases of magnon-phonon interaction. Also the magnetostriction effect of the lattice was found to play a role in this behaviour.