晶粒易轴取向度对纳米晶永磁Pr2Fe14B磁性的影响

构造了立方和不规则形状晶粒的各向异性纳米晶单相Pr₂Fe₁₄B磁体 .利用微磁学的有限元法，模拟计算了样品的磁滞回线.计算结果表明，随着磁体晶粒易轴取向度的变差， 磁体的剩磁、矫顽力均随之下降.不同晶粒尺寸的纳米晶单相Pr₂Fe_{14B磁体，其磁 性能随取向度的变化快慢不同，原因在于磁体中的晶间交换作用 (IGEC) 的强弱不同.随着 晶粒取向度的提高，纳米晶单相磁体的矫顽力逐渐增加，这完全不同于烧结磁体. 关键词： 纳米晶磁体 矫顽力 剩磁}     

纳米晶永磁Pr2Fe14B微磁学有限元法的模拟计算研究

根据实验数据，构造了接近实际纳米晶永磁Pr2Fe14B的样品，用微磁学有限元法进行了模拟计算.计算结果表明，晶界处各向异性的下降会导致矫顽力减小、剩磁值增大，而晶界处交换作用常数的减小则会使剩磁值减小、矫顽力增大.通过对实验样品的模拟研究发现，晶界处各向异性和交换作用常数的共同减小能够同时拟合出真实的矫顽力和剩磁值.模拟计算与实验在退磁曲线形状上的差距则说明模拟还存在不足. 关键词： 纳米晶永磁 磁滞回线 矫顽力 剩磁     

晶粒大小分布对纳米晶磁体Pr2Fe14B剩磁和矫顽力的影响

用微磁学有限元法计算了纳米晶磁体Pr2Fe14B的退磁曲线，文中模拟了三种具有不同晶粒大小分布的样品。计算结果表明，剩磁增强与磁体的晶粒尺寸分布情况无关而依赖于平均晶粒直径。晶粒尺寸分布对矫顽力的影响与磁体中的晶间交换耦合作用密切相关。     

纳米晶永磁Pr8Fe87B5反磁化机理研究

用熔体快淬法制备了Pr2Fe14B/α-Fe纳米复合永磁样品.测量了样品的起始磁化、反磁化过程、矫顽力和剩磁与外场的关系，以及样品的磁粘滞性.经分析认为材料的矫顽力主要由非均匀的钉扎机理决定，但由于交换硬化的软磁相的可逆转动使得这种反磁化机理不同于单相永磁材料的钉扎行为.磁粘滞性表明热激活主要源于硬磁相的不可逆磁化行为. 关键词： 纳米复合永磁 矫顽力 剩磁 磁粘滞     

PrFeB纳米晶磁体的颗粒分布对其矫顽力的影响(英文)

Nanocrystalline permanent magnets (PM) have attracted great interest because of their low rare-earth content and relatively high maximum energy production~([1-4]).Many efforts have been made to understand the effects of grain size on coercivity and remane…     

纳米晶复合Pr2 Fe14 B/α-Fe永磁材料磁性的研究

采用熔体快淬的方法制备Pr2Fe14B/α-Fe纳米晶复合永磁材料.使用振动样品磁强计(VSM)测量样品的室温磁性能.实验合金成分为(PrxFe94.3-xB5.7)0.99Zr1(其中x=8.2,8.6,9.0,9.4,9.8,10.2,10.6,11.0,11.4(原子分数,%)).系统地研究了辊速及合金成分对快淬带磁性能的影响,当Pr原子分数由8.2%-11.4%变化时,矫顽力Hci升高,但剩余磁极化强度Jr却降低了,这是导致最大磁能积(BH)max下降的原因.当x=8.2(%)时,尽管样品的Hci较低,但高的Jr使(BH)max的值达到很高,在辊速为25m/s时得到最佳磁性能为:Jr=1.37T,Hci=501.19kA/m,(BH)max=227.93kJ/m3.同时发现垂直带面方向的Jr和(BH)max远高于平行带面方向.     

纳米复合永磁材料中软磁性相交换硬化的研究

本文就纳米复合永磁材料中软磁相被交换硬化问题,从一维模型和三维模拟计算进行了分析研究. 一维和三维各向异性样品研究表明,在相同微结构下,当硬磁相的各向异性降低时,除矫顽力降低外,在磁矩全部反转之前退磁曲线是一样的. 因此,硬磁相各向异性的降低不会导致最大磁能积(BH)_max增大和剩磁增加. 对于三维各向同性样品的模拟计算表明,降低硬磁相的各向异性会使剩磁和(BH)_max都明显降低. 因此,增强硬磁相的各向异性并增大硬磁相晶粒尺寸是提高 关键词： 纳米复合永磁 矫顽力 剩磁 磁能积     

Ga替代对纳米晶Nd(Fe,Co)B黏结磁体磁性能的影响

探讨了微量的Ga替代Fe对Nd₂(Fe,Co)₁₄B/(Fe,Co)₃B+(少量)α-Fe永磁材料的晶体结构及磁性能的影响,并讨论了双相纳米晶磁体性能的变化机理以及所适用的理论模型.结果表明,Ga的添加不仅使晶粒尺寸显著变小,而且在Ga含量x<1at%的范围,随着x的增加,B_r和(BH)_max随退火时间的变化关系由形似马鞍的曲线转化为抛物曲线;矫顽力_jH_c先下降到一个最小值后再上升;当x=0.2时,综合磁性能较好 关键词： 双相纳米晶磁体 快淬 退火 交换耦合 磁性能     

R2Fe14B型永磁材料中第二磁晶各向异性常数对反磁化过程的影响

针对低温下各向同性Pr2Fe14B永磁材料的最小形核场问题,用数值计算法和近似解析解研究了第二磁晶各向异性常数K2对最小形核场的影响.研究发现,尽管对于Nd2Fe14B永磁材料一级近似的解析解与数值计算结果很接近,但是对于低温下各向同性Pr2Fe14B永磁材料则至少要用二级近似下的解析解才能与数值计算结果相接近.用有关最小形核场的计算结果很好地解释了低温时各向同性Pr2Fe14B永磁材料的矫顽力与最小形核场的关系.     

取向Pr2Fe14B与Nd2Fe14B多晶磁化曲线的计算

基于单离子晶场模型 ,提出了计算稀土 Fe(Co)金属间化合物取向多晶样品磁化曲线的方法 .用此方法计算了取向Pr2 Fe14 B和Nd2 Fe14 B多晶的高场磁化曲线 ,计算中使用了拟合化合物单晶磁化曲线得到的交换场与晶场参数 .计算曲线与实验曲线相符合 .     

Effects of the degree of grain alignment on the hard magnetic properties of sintered NdFeB magnets

r increases monotonously with an enhancement in the degree of grain alignment (i.e. decrease in the orientation coefficient σ), whereas the intrinsic coercivity _jH_c decreases monotonously. This dependence leads to a non-monotonic behaviour of the magnetic-inductive coercivity _bH_c and a saturation of the maximum energy product (BH)_max. Received: 28 August 1997/Accepted: 12 January 1998     

Studies on the magnetic properties for single-phase nanocrystalline FePt magnets with different orientation degrees

The single-phase nanocrystalline FePt magnets composed of 343 irregular-shaped grains are built. The demagnetization curves are simulated by micromagnetic finite element method. The remanence, coercivity and maximum energy product of the magnets decrease with deteriorating grain alignment. The characteristics of variation of magnetic properties with the degree of orientation are closely related to the average grain size of nanocrystalline magnets. The contribution of intergrain exchange coupling (IGEC) to remanence enhancement is associated to the degree of orientation, and decreases with improved grain alignment. With decreasing grain size, coercivity increases for anisotropic nanocrystalline magnets, which is completely different from that of isotropic nanocrystalline magnets.     

纳米晶复合Pr2Fe14B/α-Fe快淬薄带的织构与磁性

采用快淬方法制备了纳米晶复合Pr₂Fe₁₄B/α-Fe永磁薄带，研究了不同淬火速率对薄带织构和磁性的影响.通过改善快淬工艺，使得薄带中Pr₂Fe₁₄B相的晶粒在薄带的自由面形成显著的织构，Pr₂Fe₁₄B相晶粒易轴沿垂直于带面方向取向.分析了快淬凝固过程中Pr₂Fe₁₄B相的晶粒取向过程和机理，以及晶粒的大小和薄带结构的均匀性对薄带磁性的影响.对自由面有显著取向的薄带，进行酸蚀和打磨减薄处理，去除贴辊面未取向的部分，剩余部分为具有Pr₂Fe₁₄B相晶粒取向的各向异性薄带，Pr₂Fe₁₄B相取向使薄带的剩磁得到增强，矫顽力也有所提高. 关键词： 快淬 2Fe₁₄B/α-Fe永磁薄带')" href="#">纳米晶复合Pr₂Fe₁₄B/α-Fe永磁薄带 织构 磁性能     

Positive muon spectroscopy of Nd2Fe14B and Pr2Fe14B

We have performed positive muon spin rotation measurements on polycrystalline samples of Nd₂Fe₁₄B and Pr₂Fe₁₄B in zero applied field. In both samples a single sharp μSR line was observed which was unexpected in this complicated structure. The temperature dependence of the muon frequency for Nd₂Fe₁₄B clearly reflects the spin reorientation below 150 K and can be explained qualitatively by assuming that only the c-axis component of a magnetization is sampled by the muon. A smooth decrease of the muon frequency with increasing temperature is observed for Pr₂Fe₁₄B.     

Effect of hydrogenation on the magnetic properties of the intermetallic compound Er2Fe14B with single-crystal and nanocrystalline structures

Hydrogenated single crystals Er₂Fe₁₄Bh _x with different hydrogen contents are grown and their magnetic properties are studied for the first time. It is established that both the Curie temperature and the temperature of the spin-reorientation phase transition increase with an increase in the hydrogen content. In the Er₂Fe₁₄B single crystal, the contributions of the rare-earth metal and iron sublattices to the magnetic anisotropy decrease upon hydrogenation. However, their compensation occurs at a temperature higher than that in the initial compound Er₂Fe₁₄B due to the enhancement of the Fe-Fe and R-Fe exchange interactions. The effect of hydrogenation on the magnetic characteristics of the Er₂Fe₁₄B compound with a nanocrystalline structure is investigated. It is revealed that the hydrogenation leads to an increase in the coercive force and the residual magnetization of these alloys.