ON THE STATIC AND TIME-DEPENDENT MAGNETIC-PROPERTIES OF FE3O4 FINE PARTICLES - EFFECT OF OXIDATION

In this work, the results of static and time-dependent magnetization measurements on three systems of Fe3O4 fine particles are reported. Measurements of the static magnetization were carried out in the temperature range 293 K less-than-or-equal-to T less-than-or-equal-to 423 K, and of the remanent magnetization in the temperature range 5 K less-than-or-equal-to T less-than-or-equal-to 300 K over the period of time 30 s less-than-or-equal-to t less-than-or-equal-to 300 s. The remanent magnetization was found to obey the relation M = C - S ln t. Annealing the sample at 250-degrees-C was found to increase its magnetic anisotropy constant. The results were analyzed within the context of Neel's theory of magnetic clusters.