A new model of the superparamagnetic to blocked crossover behavior

DE BIASI EMILIO; ZYSLER ROBERTO DANIEL; RAMOS CARLOS ALBERTO; KNOBEL MARCELO

Río de Janeiro, Brasil

Congreso; LAW3M; 2007

In this work we present a new model that considers the thermal probability of inversion of the magnetization, through the Arrhenius law, in the thermal average of the magnetization. In the classical treatment it is supposed that the system is in thermal equilibrium independent of the temporal experimental windows. So, how is know the superparamagnetic or bloqued regimen depends of the temperature as well the measurement time. In the conventional description we assume that the system is in thermal equilibrium. Then, in this case is only possible to describe the superparamagnetic regime. We included the temporal window in the consideration of the thermal average that allowed taking in count the hysteretics behaviors and giving a “continues” description of the passage of one regime to the other. We show any numerical data, including different temporal windows and consider the high and low temperatures regimen indicating, analytically, that the propose model is in agreement whit the limit to temperature zero and infinite. Magnetization Field Cooling and Zero Filed Cooling measurements as well hysteresis loops are simulated applying this model. Some considerations were taking in count about the importance, applicability and limitations in this treatment.