具有幂次相互作用的磁性粒子凝聚过程的数值研究  

Numerical study on the aggregation of magnetic particles with power law interactions

作　　者：许晓军[1] 魏高尧[1] 蔡萍根[1] 金进生[2] 夏阿根[2] 叶高翔[2] 

机构地区：[1]浙江工业大学应用物理系,杭州310014 [2]浙江大学物理系,杭州310027

出　　处：《物理学报》2006年第8期4039-4045,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10174063);浙江省自然科学基金(批准号:Y604064)资助的课题.~~

摘　　要：在扩散限制凝聚模型的基础上引入粒子的自旋自由度(包括自旋向上和向下),并假设粒子间存在幂次Ising磁相互作用,采用MonteCarlo方法研究了在不同相互作用力程情况下磁性粒子的分形生长规律.模拟结果表明,当粒子间以反铁磁方式耦合时,凝聚体中的粒子自旋交替凝聚.当粒子间以铁磁方式耦合时,凝聚体中粒子的自旋分布与相互作用力程有关:对于短程作用系统,凝聚体中存在大小不同的自旋畴块,即为铁磁生长;而对于长程相互作用系统,凝聚体中的自旋出现反常分布,即中心区域是近似反铁磁生长的结构,其外围后续生长的粒子却保持相同自旋取向.此外,还研究了在不同相互作用力程情况下磁性分形凝聚体的形貌、磁化强度及其演化过程.We introduce in the diffusion-limited aggregation model an internal degree of freedom, i.e., a spin taking two states （up and down） with power-law Ising interaction. The fractal aggregation of magnetic particles with different ranges of interaction is investigated by Monte Carlo simulation. The simulation shows that for the antiferromagnetic coupling, the spins of the particles in the aggregates tend to be oriented alternately. For the ferromagnetic coupling, however, the spin orientation distribution of the aggregates depends on the interaction range： for the short-range interaction, domains with different sizes are observed in the aggregates, i.e., the aggregates exhibit ferromagnetic structure; for the long-range interaction, during the earlier stage of the growth process, the aggregates exhibit approximately antiferromagnetic structure, then, in subsequent growth of the outer part of the aggregates, the spin states of all particles are similar. The morphology and magnetization of the magnetic fractal aggregates as well as their evolutions with different ranges of interaction are also studied.

关 键 词：幂次相互作用 扩散限制凝聚模型 自旋 

分 类 号：O469[理学—凝聚态物理]