纳米晶Nd-Fe-B基稀土永磁体的磁性能的微磁量子理论计算

MICOMAGNETICS AND QUANTUM MECHANICAL CALCULATION OF THE MAGNETIC PROPERTIES FOR NANOMATERSCALE RARE-EARTH MAGNETS

从微磁学理论出发，利用铁磁体总自由能极小的变分法，导出了取向各向异性磁体的磁化强度满足的Ｂｒｏｗｎ方程，对取向的纳米晶双相交换耦合磁体，该方程类似于量子力学中的定态Ｓｃｈｒｄｉｎｇｅｒ方程，利用中心场问题的求解方法推导了Ｎｄ－Ｆｅ－Ｂ基稀土永磁体的成核场同时随两相晶粒尺寸的变化关系。数值计算结果表明，当两相晶粒尺寸小于某一临界尺寸时，可以获得磁性能优异的纳米晶稀土永磁体。所得结果可用于定性解释实验结果和指导巨磁能积纳米晶永磁体的制备。

Based upon micromagnetics and the variational method of the total free energy of the magnets, we derived Brown equation of the magnetization for the aligned two-phase magnets. In the case of this kinds of magnets, the Brown equation is similar to static Schordinger equation. By means of the method of resolving the contral-field problem, we obtained the dependence of the nucleation field of the exchange-coupling magnets varys with the particle sizes of both soft and hard magnet phase. After numerical calculation, it's shown that the excellent permanent magnetic porperties are obtained when the two-phase particle sizes are smaller than the critical sizes. The present calculation results can be used to explain the known experimental results and direct the pareparing of the giant-energy product permanent materials.