Energy Barrier, Coercivity and Blocking Temperature Variation of Fine-Particle Systems

Jing-Ju Lu ； Huei-Li Huang

《Chinese Journal of Physics》 38卷1期 (2000/02) Pp. 81-94

並列摘要

Coercivity and energy barrier height variation of a dipole interacting fine particle system has been evaluated by means of the fixed step Monte Carlo simulation supplemented by a perturbation calculation. The dipole interaction field can be decomposed into a longitudinal and a transverse field component. The superposition of the two field component leads to local maxima at β = 0 and π/2 and a global minimum of coercivity at β～ 60^±. Thus, the coercivity of a random dipole interacting system generally becomes lower compared to that of a noninteracting system since the probability of finding the bonding angle of the system smaller than 30^± is less than 13%. The asymmetric fanning mode is shown to be favored in comparison with the other modes in making the (↑↓) ⇒ (↓↓) transition if β is neither zero nor π/2. Whenever the bonding angle is close to π/2, the system may exhibit a two-step switching behavior causing the system to broaden its switching field distribution. Finally, the fieldcooled and zero-field-cooled magnetization relaxation behavior and its blocking temperature distribution can be well accounted for.