Interaction effects on the time dependence of the magnetization in recording particles

The influence of the magnetostatic interactions on the time dependence of the magnetization of assemblies of particles, which are used in magnetic recording, with various packing fraction is analyzed. The time effects are studied with measurements of magnetization decay and deduction of magnetic viscosity S, fluctuation field H-f, and activation volume V-ac. The magnetostatic interactions among the particles are evaluated with measurement of the Delta M deviations from the Wohlfarth equation and calculation of the ''Delta plot area,'' which expresses the overall effect of the interactions. The experimental results show a general weakening of time effects with the increase of packing and interactions. The magnetization decay, S and H-f decrease, and V-ac increases, when p or Delta plot area increase. The strengthening of the interactions supports the thermal stability of the particle magnetization. The result is discussed in relation to the evolution of the magnetization reversal induced by the presence of interactions, which make the occurrence of a coherent switching mode more probable. (C) 1997 American Institute of Physics.