Y(TiFe)12的中子衍射研究

用中子衍射研究了Y(TiFe)₁₂的晶体结构及其磁的特性。观测到Y(TiFe)₁₂为ThMn₁₂型结构,空间群为14/mmm,Fe和Ti分布在三个不等效的晶位上,且Fe和Ti分别择优占据某些晶位。对所得结果进行了初步讨论。 关键词：     

新型金属间化合物R_2Fe_(17)N_(2.4)的结构与磁性

本文采用适当的热处理,使氮原子进入到R_2Fe_(17)的结构中去.利用X射线衍射、磁测量和中子衍射技术研究了R_2Fe_(17)N_(24)的晶体结构和内禀磁性及其之间的联系.中子衍射研究结果表明,氮原子在Th_2Zn_(17)型菱方结构中,占据9e间隙位置.氮的加入使晶胞体积增大、Curie温度升高;使铁原子3d电子正负能带电子数目差额扩大、饱和磁矩增强;并且氮原子对稀土晶位的晶场效应有重大影响,导致Sm_2Fe_(17)N_(24)具有易磁化轴.所有这些效应使得Sm_2Fe_(17)N_(24)具备了研制高矫顽力永磁体的内禀性能.     

用于凝聚态物质研究的旋转晶体中子飞行时间谱仪

本文介绍了我所自行设计和制造的一台旋转晶体中子飞行时间谱仪。该仪器对凝聚态物质的各种动力学研究是一个有效的工具。我们通过选取适当的锗单晶(111)平面旋转轴的办法消除了仪器单色束中多晶面反射的“污染”(contamination)。该谱仪的入射初始中子能量范围可为10—100meV,对应的初始中子能量分辨率为2.5—7.2％。本文根据Brockhouse理论对散射中子的分辨率作了详细的理论计算,并将计算结果与实测结果进行了对比。介绍了标准钒样品的非弹性散射中子谱的测量结果并与国外几个同类型谱仪的基本特性作了比较。     

宇宙射线的起源

不少的书籍讲述了宇宙射线,许多研究者在这个领域中工作着,他们已经研究了宇宙射线的许多性质。然而,关于宇宙射线这个自然现象的起源这样一个重要的、长久以来就使科学家们感到烦恼的问题,直到目前还没有最终地得到解决。由宇宙空间射进大气层来的原始宇宙射线乃是一些以接近光速的速度运动着的荷电粒子流。其中最多的是质子,亦即氢原子核。在宇宙射线中也发现了一些较重的元素的核:氦核     

CRYSTALLOGRAPHIC STRUCTURE AND MAGNETIC PROPERTIES OF R_(2)Fe_(17)N_(2.4)

By a proper thermal treatment, the nitrogen atoms can enter the R2Fe17 structure. The crystallographic and intrinsic magnetic properties as well as their relationship have been studied by magnetic measurements, X-ray and neutron diffraction techniques. The neutron data indicate that the nitrogen atoms occupy the interstitial sites in the Th2Zn17-type rhom-bohedral structure. The inserting nitrogen atoms are found to dilate the cell volume, increase the Curie temperature and enhance the saturation moment by raising the difference in the electron number between the spin-up and spin-down 3d subbands of the Fe atoms. Furthermore, the nitrogen atoms have an important effect on the magnetocrystallic anisotropy, which results in an easy axis with Sm2Fe17N2.4. All these make Sm2Fe17N2.4 favorable for permanent magnet applications.     

Nb对C-15相V_2Zr和V_2(HfZr)系列声子性能的影响

本文用中子飞行时间方法对C-15相的超导物质V_2Zr,V_2Zr_(0.95)Nb_(0.05)及V_2Hf_(0.5)Zr_(0.5),V_2Hf_(0.5)Zr_(0.3)Nb_(0.2)的热中子非弹性散射谱作了测量,发现Nb的添加对V_2Zr和V_2Hf_(0.5)Zr_(0.5)系列的作用不同,V_2Zr添加第三组元Nb后,超导临界温度Tc增加,声子频率“软化”,而V_2Hf_(0.5)Zr_(0.5)系列添加第四组元Nb后,Tc略有下降,声子频率则“硬化”。V_2Zr_(0.95)Nb_(0.05)声子频率比V_2Zr“软化”的结果与以前磁化率下降几何平均声子频率上升的结果不一致。对于V_2Hf_(0.5)Zr_(0.5)加Nb后声子频率“硬化”的现象用角动量分波表象的能带论方法分析电-声作用得出的杂化理论作了解释     

Nb对C-15相V2Zr和V2(HfZr)系列声子性能的影响

本文用中子飞行时间方法对C-15相的超导物质V₂Zr,V₂Zr_0.95Nb_0.05及V₂Hf_0.5Zr_0.5,V₂Hf_0.5Zr_0.3Nb_0.2的热中子非弹性散射谱作了测量,发现Nb的添加对V₂Zr和V₂Hf_{0.5 关键词：}     

CRYSTALLOGRAPHIC STRUCTURE AND INTRINSIC MAGENTIC PROPERTIES OF R2Fe14BNx

We found that the nitrogen atoms can enter into the R₂Fe₁₄B structure by a proper heat treatment in nitrogen atmosphere. The crystallographic structure and magnetic properties of R₂Fe₁₄BN_x, R =Nd and Y, have been investigated by using X-ray and neutron diffraction techniques as well as magnetic measurements. The neutron diffrac-tion data show that the nitrogen atoms occupy the 4f interstices. The interstitial nitrogen atoms were found to have an effect of enhancing Curie temerature, whereas, decreasing saturation magnetization and magneto-crystalline anisotropy. The rela-tionship of the crystal structure and the intrinsic magnetic properties of this crystal is discussed.     

CRYSTALLOGRAPHIC STRUCTURE AND INTRINSIC MAGENTIC PROPERTIES OF R2Fe14BNx

We found that the nitrogen atoms can enter into the R₂Fe₁₄B structure by a proper heat treatment in nitrogen atmosphere. The crystallographic structure and magnetic properties of R₂Fe₁₄BN_x, R =Nd and Y, have been investigated by using X-ray and neutron diffraction techniques as well as magnetic measurements. The neutron diffrac-tion data show that the nitrogen atoms occupy the 4f interstices. The interstitial nitrogen atoms were found to have an effect of enhancing Curie temerature, whereas, decreasing saturation magnetization and magneto-crystalline anisotropy. The rela-tionship of the crystal structure and the intrinsic magnetic properties of this crystal is discussed.