磁性颗粒复合体磁渗流区矫顽力异常的研究

制备了MnZn铁氧体/SiO₂颗粒复合体.研究了磁性颗粒复合体的有效磁导率μ、 比磁化强度σ以及矫顽力H_c随磁性颗粒含量的变化.研究发现，在MnZn铁氧体体积百分含 量为90%—98%的区域，复合体的有效磁导率μ的变化速率发生突变，出现磁渗流现象，从实验得到的体系磁渗流阈值V_c=97.9%.在磁渗流区，矫顽力表现出异常行为.结果表明 ，这种异常行为与复合体微观结构有着密切关系.在磁渗流前，矫顽力H_c的变化主要来 源于磁关键词：颗粒复合体磁渗流矫顽力

Abnormal coercivity behaviour in the magnetic percolation region of a magnetic g ranular composite

MnZn-ferrite/SiO₂ particle composites are prepared by mechanical ball ing. We study the relations of effective permeability μ, specific magnetization σ and coercivity H_c with the MnZn-ferrite concentration. The results indicate that an abrupt change emerges in effective permeability when the volume percentage of MnZn-ferrite particles is near V=98%, which means that a magnetic percolation phenomenon occurs in the system. Meanwhile, it is found that the coercivity H_c exhibits an anomalous behaviour that depends strongly on the microstructure of the composite. Above the percolation threshold, the variation of coercivity can be mostly explained in terms of dipolar interaction between magnetic particles, whereas below the percolation threshold, the decrement of H_c is ascribed dominantly to increasing specific magnetization σ. At the same time, we determine the measured percolation threshold V_c=97. 9%, which can be derived from the maximum of d²μ/dV².