Magnetic particle-particle interaction in frozen magnetic fluids

Magnetic resonance is used to study magnetic dipole particle-particle interaction in ionic water-based iron-manganese magnetic fluids. A set of six samples having particle concentration running from to 1.2X10(16) to 6.3X10(16) particles/cm(3) were frozen below room temperature and analyzed in the range of 100-250 K. Average values of magnetic particle-particle interaction energy were obtained from the temperature dependence of the resonance linewidth broadening. At 1.2X10(16) particles/cm(3) magnetic particle-particle interaction energy is found to be of the order of 1.2 meV, However, at 6.3X10(16) particles/cm(3) magnetic particle-particle interaction energy goes to 32 meV. The enhancement of the magnetic particle-particle interaction energy far beyond the linearity is associated to cluster structuration. A one-dimensional model for cluster structuration is presented. (C) 1996 American Institute of Physics.