Effects of the grain size distribution on magnetic properties of magnetite: constraints from micromagnetic modeling  

作　　者：Kunpeng Ge Qingsong Liu 

机构地区：[1]Palaeomagnetism and Geochronology Laboratory (SKL-LE),Institute of Geology and Geophysics, Chinese Academy ofSciences [2]University of Chinese Academy of Sciences

出　　处：《Chinese Science Bulletin》2014年第34期4763-4773,共11页

基　　金：supported by the National Natural Science Foundation of China(41025013 and 41374073)

摘　　要：Magnetite is the most important magnetic mineral in paleomagnetism. Its magnetic properties are controlled by many factors, such as grain size distribution,shape and interactions. Traditional rock magnetic experiments, however, have great difficulty in decoupling the effects of these parameters. In this study, we attempted to investigate the effects of grain size distribution on magnetic properties of magnetite powders by using a micromagnetic method. The particle geometries used in the micromagnetic model were based on the grain size distribution observed in a synthetic magnetite powder. The simulated hysteresis parameters agree well with the experimental measurements and provide clear microstructures of the magnetic remanence. Our results show that grain size plays a more important role in affecting hysteresis parameters of magnetite assemblages than shape under effects of interactions. Uniform or vortex superstates formed by two or more particles are found and display different stabilities of magnetic recording in assemblages.Some domain structures of single-domain(SD) particles are reversed as the applied field decreases to zero. Small pseudo-single-domain particles behave as SD structures and may dominate the magnetic recordings. In all, micromagnetic modeling of grain size distributions provide a better understanding of magnetic assemblages consisting of nanoscale particles.Magnetite is the most important magnetic mineral in paleomagnetism. Its magnetic properties are controlled by many factors, such as grain size distribution, shape and interactions. Traditional rock magnetic experiments, however, have great difficulty in decoupling the effects of these parameters. In this study, we attempted to investigate the effects of grain size distribution on magnetic properties of magnetite powders by using a micromagnetic method. The particle geometries used in the micromagnetic model were based on the grain size distribution observed in a synthetic magnetite powder. The simulated hysteresis parameters agree well with the experimental measurements and provide clear microstructures of the magnetic remanence. Our results show that grain size plays a more important role in affecting hysteresis parameters of magnetite assemblages than shape under effects of interactions. Uniform or vortex superstates formed by two or more particles are found and display different stabilities of magnetic recording in assemblages. Some domain structures of single-domain （SD） particles are reversed as the applied field decreases to zero. Small pseudo-single-domain particles behave as SD structures and may dominate the magnetic recordings. In all, micromagnetic modeling of grain size distributions provide a better understanding of magnetic assemblages consisting of nanoscale particles.

关 键 词：磁性矿物 磁铁矿 磁模拟 粒度分布 晶粒尺寸分布 几何形状 微观结构 颗粒大小 

分 类 号：P318.4[天文地球—固体地球物理学] P578.24[天文地球—地球物理学]