纳米晶永磁材料晶间交换耦合作用的模拟计算研究

Investigation of intergrain exchange coupling interaction of nanocrystalline permanent magnets by numerical simulation

利用微磁学有限元法 ,模拟计算了单相和复相各向同性纳米晶磁体的起始磁化曲线、退磁曲线和回复曲线 .验证了用δm(H)曲线的正峰值来衡量纳米晶磁体晶间交换耦合作用的有效性 .计算结果表明 ,纳米晶单相和复相磁体的晶间交换耦合作用都随晶粒尺寸的增加而降低 ,当晶粒尺寸过大时复相磁体表现出两相行为 ,其δm(H)曲线出现了两个正峰值 .分析表明 ,外场较小的正峰值是软磁相与硬磁相晶粒之间交换耦合作用的结果 。

The initial curves,demagnetization curves and recoil curves of Pr 2Fe 14 B and Pr 2Fe 14 B/α-Fe nanocrystalline permanent magnets have been calculated by micromagnetic finite-element method. The validity of δ m(H) curves,which can be used to determine the strength of intergrain exchange coupling interaction (IGEC),is approved by the calculated results. It is found that IGEC weakens with increasing grain size D for single-phase nanocrystalline and nanocomposite permanent magnets. Thus,the demagnetization curve shows a two-phase behavior and the δ m(H) curve shows two peaks for the nanocomposite sample with D =20?nm. The peak at small field can be attributed to the exchange interaction between the magnetic hard and soft grains,while the peak at large field may be due to the IGEC among hard grains.