金属间化合物Ho_2Co_(17-x)Si_x的各向异性机制研究

研究了非磁性原子 Si替代 Co对 Ho2 Co1 7金属间化合物结构和磁性的影响。 X射线衍射分析表明 ,所有 Ho2 Co1 7- x Six(x=0 .5 ,1.0 ,1.5 ,2 .0 ,2 .5 ,3.0 )化合物都为 Th2 Ni1 7型六角结构 ;化合物的晶格常数和单胞体积都随 Si含量的增加而呈线性下降。磁性测量表明 ,Ho2 Co1 7- x Six 化合物的饱和磁化强度随 Si含量的增加而呈线性下降。从热磁曲线测量观察到 ,Ho2 Co1 7- x Six 化合物在 x=0 .5时呈面各向异性 ,当 1.0≤ x≤ 3.0时出现由易面到易轴的自旋重取向 ,自旋重取向温度 Tsr随 Si原子含量的增加先下降 ,而后又上升 ,在 x=2 .5处出现最低点。     

Sm2（Fe1—xTix）17组织结构及其氮化物各向异性磁粉磁性能研究

敏感度是系统鲁棒特性的主要指标，对于控制对象存在较大模型化误差的伺服系统来说，必须具有低敏感度特性。本文应用二自由度控制理论和敏感度特性，设计出了对控制对象的模型化误差不敏感的低敏感度伺服系统，并采用８０９８单片机实现了数字化低敏感度伺服补偿器。     

Cu/Fe金属超晶格磁晶各向异性的研究

借助磁转矩仪对Ｃｕ／Ｆｅ金属超晶格（ＭＳＬ）的磁晶各向异性进行了研究。测量了其一维周期（１－ＤＰ）和一维准周期（１－ＤＱＰ）ＭＳＬ在室温（２９４Ｋ）和低温（７７Ｋ）的转矩曲线，计算了它们的单轴异性常数Ｋμ，发现与（１－ＤＱＰ）ＭＳＬ磁晶各向异性反常，１Ｋμ显著增大，但两种温度下的Ｋμ均〉０，出现垂直膜面各向异性，而且无论是（１－ＤＰ）ＭＳＬ，还是（１－ＤＱＰ）ＭＳＬ，其磁晶各向异性随温度升高而减小     

金属间化合物Ho2Co17-xSix的各向异性机制研究

研究了非磁性原子Si替代Co对Ho2Co17金属间化合物结构和磁性的影响.X射线衍射分析表明,所有Ho2Co17-xSix(x=0.5,1.0,1.5,2.0,2.5,3.0)化合物都为Th2Ni17型六角结构;化合物的晶格常数和单胞体积都随Si含量的增加而呈线性下降.磁性测量表明,Ho2Co17-xSix化合物的饱和磁化强度随Si含量的增加而呈线性下降.从热磁曲线测量观察到,Ho2Co17-xSix化合物在x=0.5时呈面各向异性,当1.0≤x≤3.0时出现由易面到易轴的自旋重取向,自旋重取向温度Tsr随Si原子含量的增加先下降,而后又上升,在x=2.5处出现最低点.     

金属间化合物Tb2Co17-xMnx的结构与磁性研究

研究了 Mn替代 Co对 Tb2 Co1 7金属间化合物结构和磁性的影响。 X射线衍射表明 :Tb2 Co1 7- x Mnx(x=0 ,1,2 ,3,4)化合物均为 Th2 Zn1 7型菱方结构 ;晶胞参数和单胞体积均随 Mn含量的增加而线性增大。磁性测量表明 :Tb2 Co1 7- x Mnx(x=0 ,1,2 ,3,4)化合物室温为面各向异性 ;居里温度 Tc随 Mn含量 x的增加而线性降低 ;自旋重取向温度 Tsr随 Mn含量 x的增加而线性降低 ;饱和磁化强度 Ms起初随 Mn含量增加而缓慢增大 ,当 x>3时随 Mn含量增加而迅速减小。     

高温稀土永磁Sm2(Co,Cu,Fe,Zr)17的烧结工艺

通过改变烧结工艺制度,制备了高温稀土永磁Sm(Cobal Fe0.26Cu0.05Zr0.026)70,其磁性能和温度系数(β)分别为:Br为1.08T,Hci为2 286 kA/m,Hcb为932 kA/m,(BH)max为220.8kJ/m3;β为-0.19%/℃.研究表明:提高烧结温度或真空预烧温度都可使材料的性能明显提高,特别是用后者制得的材料拥有较高的矫顽力和低的温度系数,具有较好的高温性能.然而,烧结温度或真空预烧温度过高时,Sm会从基体相中析出,使材料的磁性能降低,而且烧结温度过高还会使晶粒长大,导致材料矫顽力降低.     

冷轧无取向硅钢的磁晶各向异性能的模拟

根据冷轧无取向硅钢的磁晶各向异性能与织构的关系,通过织构取向分布函数ODF程序的计 算,得到取向分布函数的C系数和磁晶各向异性能分布函数MDF的M系数,计算了0.004% C、0. 33% Si无取 向硅钢在宏观各个方向上的磁晶各向异性能。模拟结果表明,多晶体材料的织构影响磁晶各向异性能,当 ｛111｝〈112〉织构组分密度较低时,磁晶各向异性能较小     

Pr2Fe17-xAlx系列化合物的结构与磁熵变

采用熔炼法制备了Pr2Fe17-xAlx系列化合物。利用X射线衍射和MPMSXL-7型磁强计对样品相结构和磁熵变进行了研究。结果表明：Pr2Fe17-xAlx系化合物保持了Th2Zn17型菱方结构，其居里温度可通过成分微调达到室温附近；Pr2Fe17-xAlx系化合物在居里点附近发生的相变属于二级相变，并在较宽温区范围内保持了较大的磁熵变。该化合物在2．0T外场下的最大磁熵变达到纯金属Gd的60％左右，且其化学性质稳定，制冷温区宽，价格低，是一类具有较大应用潜力的新型室温磁制冷工质材料。     

高温稀土永磁Sm2(Co,Cu,Fe,Zr)17的研制

利用粉末冶金方法研制了Sm(CobalFe0.24Cu0.08Zr0.027)7.0,Sm(CpbalFe0.27Cu0.05Zr0.027)7.0,Sm(CobalFe0.26Cu0.05Zr0.026)7.0 3种高温永磁,并对其磁性能、温度稳定性和显微结构进行了分析.结果表明:样品Sm(CobalFe0.27Cu0.05Zr0.027)7.0具有最高的内禀矫顽力(2 165.6 kA·m-1)和最大磁能积(212.0kA·m-3);3种磁体的温度系数都较低,最高使用温度均在400℃以上,大大高于一般商用磁体;增加Sm,Co,Cu的含量和减少Fe的含量可以提高材料的温度稳定性.X射线分析表明,合金中含有Sm2(Co,Fe)17主相,Sm(Co,Cu)5相,含Zr化合物等.Sm(Co,Cu)5相、单质Zr、晶粒边界等钉扎畴壁,使合金具有较高的矫顽力.     

Rare earth permanent magnets Sm2(Co,Fe,Cu,Zr)17 for high temperature applications

Sintered Sm(CobalFexCu0.1Zr0.03)7.5 (x=0.09-0.21) permanent magnets with higher Fe content were found to have higher remanence Br and maximum energy product (BH)max at room temperature. Br and (BH)max reached maximum of 0.96 T and 176.7 kJ/m3, respectively at room temperature when the Fe content x reached 0.21. However, the intrinsic coercivity Hci at room temperature increased gradually when the Fe content x increased from 0.09 to 0.15, but when x further increased to 0.21, Hci decreased. Hci attained its peak value of 2276.6 kA/m with Fe content x=0.15 at room temperature. For magnets with x=0.15, Br, (BH)max and Hci reached 0.67 T, 81.2 kJ/m3 and 509.4 kA/m at 500℃, respectively, showing good high temperature stability, which could be used in high temperature applications.     

Rare earth permanent magnets Sm2（Co,Fe, Cu,Zr）17 for high temperature applications

Sintered Sm（Coba1FexCu0.1Zr0.03）7.5 （x=0.09-0.21） permanent magnets with higher Fe content were found to have higher remanence Br and maximum energy product （BH）max at room temperature. Br and （BH）max reached maximum of 0.96 T and 176.7 kJ/m^3, respectively at room temperature when the Fe content x reached 0.21. However, the intrinsic coercivity Hci at room temperature increased gradually when the Fe content x increased from 0.09 to 0.15, but when x further increased to 0.21, Hcidecreased. Hci attained its peak value of 2276.6 kA/m with Fe content x=0.15 at room temperature. For magnets with x=0.15, Br, （BH）max and Hc1 reached 0.67 T, 81.2 kJ/m^3 and 509.4 kA/m at 500 ℃, respectively, showing good high temperature stability, which could be used in high temperature applications.     

RE_2(CoFe)_(17-x)Ti_x型合金的结构和磁性(RE=Nd,La)

用电子探针 (EPMA)、X射线衍射仪和 2 0T脉冲强磁场测试仪研究了RE2 (CoFe) 1 7-xTix(RE =Nd ,La)的结构与磁性。结果表明 ,Nd2 Co1 7-xTix经过 10 5 0℃× 15h均匀化处理 ,在x =1时 ,Nd2 Co1 7型化合物变成Nd(CoTi) 1 2 和Nd2 (CoTi) 7型化合物 ,而呈现出单轴各向异性。此时合金的饱和磁化强度为 0 .7T ,各向异性场为 2 2 5 0 .3kA·m- 1 。对La Co Fe Ti2∶17型合金的磁特性进行了研究。随着铁含量的增加 ,合金的饱和磁化强度明显增加 ,但也明显地降低了各向异性场     

RECo_(10)V_2(RE=Y,Gd)化合物中的磁作用

用两格点分子场理论分析了RECo1 0 V2 (RE =Y ,Gd)化合物的磁矩随温度的变化。采用数值拟合的方法计算出了描述 3种磁作用的分子场系数nRECo,nCoCo和nRERE,并且计算出了居里温度TC。对于YCo1 0 V2 ,分子场理论仅以nCoCo给出了很好的描述。而对于GdCo1 0 V2 ,3个分子场系数中nCoCo最大 ,这意味着磁作用主要由钴 3d电子间的交换所支配。另外 ,为了便于分析磁晶各向异性能与温度的关系 ,本文还给出了分子场强度随温度变化的曲线     

Sm2(Fe,M)17Nx稀土永磁材料的研究进展

综述了Sm2(Fe，M)17Nx永磁材料的最新研究进展，介绍了Sm2(Fe，M)17Nx磁粉及磁体的制备技术，说明用其他元素替换Sm或Fe对材料性能的影响，以及粉末颗粒具有最佳的尺寸和形貌的重要性。并指出放电等离子烧结技术(SPS)有望成为制备Sm2(Fe，M)17Nx致密磁体的一个有效方法。     

Paramagnetic Anisotropy of CdGd2(WO4)4-δ Single Crystal

CdGd2(WO4)4-δ single crystal was grown using the Czochralski's method. The crystal structure was tetragonal scheelite with lattice parameters a=b=0.5203 nm and c=1.1359 nm. There were vacancies of (WO4)2-, therefore, there were some Gd2+ ions. Langevin paramagnetism and anisotropy were observed from the σ-T curves at room temperature. The susceptibility χ// was 3.5018×10-3, and χ⊥ was 3.4403×10-2. The anisotropy was also observed in the electron spin resonance (ESR) experiments. The anisotropic Landé factors were g//=2.1333 and g⊥=2.8411. The direction of easy magnetization was in the a-b plane. Anisotropic paramagnetic Curie constants C// and C⊥ were not only related to macroscopic σ that was observed through the experiment, but were also related to J⊥ and J//, which were the microscopic quantum numbers of the Gd2+ and Gd3+ ions. Based on the detailed analyses, the proportion of 36.8% of Gd3+ ions to 63.2% of Gd2+ ions in the Gd ions of the CdGd2(WO4)4-δ crystal was calculated, and δ was 0.638 in the single crystal.     

Magnetic Properties and Molecular Field Analysis of （ Ce, Nd） 2 （Fe, Si, Mn） 17 Compounds

The temperature-dependent magnetization of the ( Ce, Nd) 2 (Fe, Si, Mn) 17 intermetallic compounds were measured and analyzed by molecular field theory (MFr). The relationship between Tc and the intrasublattice coupling interactions was discussed. The two-sublattice MFT model can well describe the temperature dependence of the magnetization for all the compounds investigated. Ce ion in (Ce, Nd)2Fel7 compounds does not simply dilute the magnetic structure, but is likely present in a mixed-valence state. The substitution of Si for Fe strongly raises Tc and the mean Fe moment remains unchanged for Ce2(Si, Fe)17 compounds, and the 3d exchange coupling constant JFF increases linearly. Mn decreases Tc of Nd2(Mn, Fe)17 compound by reducing JFF。