三维晶粒尺寸及分布对纳米永磁材料磁性能的影响

本文建立厚度为d的晶粒间界相均匀包围边长为D的三维立方体模型.假定晶粒间界相削弱了晶粒间的交换耦合相互作用.研究了晶粒尺寸及分布对纳米永磁材料有效各向异性及矫顽力的影响.结果表明：单个晶粒的平均各向异性随晶粒尺寸D的增大而增大.且材料的有效各向异性Keff和矫顽力Hc均随平均晶粒尺寸的增大而上升,而上升速率逐渐减慢.Keff和Hc随分布系数的增加而下降,且下降速率逐渐减慢.当Pc=0.7,=1.5,K1（0）=0.2Kh,d=2nm时,我们计算的矫顽力与实验数值符合地很好（Pc是无量纲因子,在0到1之间取值.Kh是晶粒内部正常的磁晶各向异性常数,K1（0）和d分别为晶粒间界相的各向异性常数和厚度）.

Dependence of magnetic properties on three dimension grain sizes and distribution for nanometer permanent magnetic material

Constructed a theoretical model that the intergranular phase uniformly surrounds three dimension grain cube with each edge of D. Supposed that intergranular phase weakening intercrystalline exchange coupling interaction. Effects of grain sizes and distribution on the effective anisotropy and coercivity are investigated for nanometer permanent magnetic material. The results indicate that the single grain average anisotropy 〈K〉 increases with increasing grain size D. And the effective anisotropy Keff and coercivity Hc increase, but ratcheting rate decreases as average grain size 〈D〉 increases. However, the Keff and Hc decreases, and dropping rate reduces with increasing distribution coefficient s. When Pc=0.7, s=1.5, K1（0）=0.2Kh, d=2 nm, our calculated coercivity is consistent with the experimental data （Pc is dimensionless constant, and its values between 0 and 1. Kh is the normal anisotropy constant in inside of grain, K1（0） and d are intergranular phase anisotropy constant and thickness, respectively）.