永磁性大块金属玻璃Nd60Al10Fe20Co10低 温磁性的研究

研究了Nd₆₀Al₁₀Fe₂₀Co₁₀ 大块金属玻璃 磁性随温度的变化关系，结果表明Nd₆₀Al₁₀Fe₂₀Co₁₀ 在室温下 表现为永磁性，随着温 度的降低，矫顽力和磁滞回线形状都有很大的变化.交流磁化率在18 K左右出现尖峰而且峰 值温度随频率变化，表明该大块非晶体系中存在自旋玻璃态. 关键词： 大块金属玻璃 低温磁化率 自旋玻璃     

压力下 Nd60Al10Fe20Co10块体金属玻璃的弹性行为

室温下在等静压最高达～0.5GPa的条件下,利用超声回波技术测量了超声波横波和纵波在Nd60Al10Fe20Co10块体金属玻璃中的传播时间来确定横波和纵波速度.测量时所采用的超声波频率为10MHz.利用所测量的数据,建立了超声波波速、样品的密度、弹性模量以及Debye温度等与所施加的压力之间的相互关系.并且推导出Murnaghan状态方程.另外,基于非晶态与晶态物理性能的相似性,对此块体非晶的压缩曲线、弹性常数和Debye温度等进行了理论计算,结果表明Nd60Al10Fe20Co10块体金属玻璃的弹性性能与其组成的元素有着密切的关系.     

复相Nd4.5Fe76.3Ga0.3Co1.0B18合金的结构与磁性

利用快淬法制备了Nd_4.5Fe_76.3Ga_0.3Co_1.0B₁₈非晶合金,晶化处理后获得主相为Fe₃B与Nd₂Fe₁₄B的纳米晶永磁材料.采用X射线衍射、透射电子显微镜及磁测量手段分析研究了材料的微观结构与磁性能,并通过测量磁体的δM曲线,研究了晶粒间的交换耦合作用及其与微观结构、磁性能的关系. 关键词：     

(Nd1－xGdx)3Fe27.31Ti1.69化合物的结构和磁性

通过X射线衍射和磁性测量等手段研究了(Nd_1-xGd_x)₃Fe_27.31Ti_1.69(0≤x≤0.6)化合物的结构和磁性.X射线衍射测量结果表明Gd替代后并未改变Nd₃(Fe,Ti)₂₉化合物的晶体结构，但引起了晶胞体积收缩.随着Gd含量的增加，化合物的居里温度T_C和室温磁晶各向异性场B_a单调增加，而自旋重取向 关键词： 1-xGd_x)₃Fe_27.31Ti_1.69化合物')" href="#">(Nd_1-xGd_x)₃Fe_27.31Ti_1.69化合物 磁晶各向异性 自旋重取向 磁相图     

快淬Nd3.6Pr5.4Fe83Co3B5薄带的反磁化行为和磁黏滞性

用电弧熔炼法制备了Nd_3.6Pr_5.4Fe₈₃Co₃B₅合金铸锭,然后利用熔旋快淬法在铜辊转速V=20m/s下制备了Nd_3.6Pr_5.4Fe₈₃Co₃B₅薄带.快淬带主要由软磁相α-Fe和Nd₂Fe₁₄B型的硬磁相组成.采用直流退磁剩磁曲线方法分析了样品在反磁化过程中的可逆与不可逆磁化部分,并研究了软磁相和硬磁相的反磁化行为,得到样品的不可逆磁化形核场H_no约为440kA/m.同时研究了样品的磁黏滞性,结果表明由于软磁相的存在使得热激活体积较大. 关键词：     

块体金属玻璃Zr46.75Ti8.25Cu7.5Ni10Be27.5的超导与负电阻温度系数

测量了块体金属玻璃Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_27.5在退火前后其电阻值随温度的变化,测量的温度范围为1.5—300K.样品在退火前后都发现有超导现象.零磁场下其超导转变温度T_c分别为1.84和3.76K.在5—300K温度范围内,原始样品具有负的电阻温度系数.如果取Zr, Ti, Cu, Ni及Be分别贡献出1.5, 1.5, 0.5, 0.5及两个传导 关键词： 块体金属玻璃 超导 电阻温度系数     

非晶态Gd45Ni30Al15Co10合金的制备与磁热性能

具有优良磁热性能的材料是磁制冷技术应用的关键.本文设计制备出了一种非晶态四元Gd₄₅Ni₃₀Al₁₅Co₁₀合金条带,系统地研究了该合金的磁热性能. Co的引入增加了合金的非晶态热稳定性,扩大了过冷液相区宽度. Gd₄₅Ni₃₀Al₁₅Co₁₀非晶态合金条带的居里温度和有效磁矩分别为80 K和7.21μB,在10 K温度下饱和磁化强度达到173 A·m~2·kg^-1,矫顽力为0.8 kA·m^-1,具有优异的软磁性能.在5 T的外加磁场下, Gd₄₅Ni₃₀Al₁₅Co₁₀非晶态合金的磁熵变峰值和相对制冷能力分别高达10.2 J·kg^-1·K^-1和918 J·kg^-1.该合金具有典型的二级磁相变特征,可以在较宽的温度范围...     

热处理对非晶态合金Nd4Fe96-xBx磁性的影响

本文研究了用单辊急冷方法制备的非晶态合金Nd₄Fe_96-xB_x的晶化,以及热处理对其硬磁性和相组成的影响,发现非晶态合金Nd₄Fe_96-xB_x的晶化温度比相同B含量的非晶态合金Fe_100-xB_x高120—190K,X射线衍射和热磁测量表明,15≤x≤25的样品晶化相是由Nd₂Fe₁₄B(T 关键词：     

Si对Nd2Fe14B四方相结构和磁性的影响

本文对Si加入Nd₂Fe₁₄B四方相后所形成的合金相的结构和磁性进行了研究。结果表明,Si加入Nd₂Fe₁₄B四方相后并不破坏它的结构(Si的含量可达B的两倍),而形成Nd₂(Fe,Si)₁₄B赝三元金属间化合物。随着Si含量的增加,晶格常数和饱和磁化强度随之减小,但居里温度则随之增加。Si的加入,并不改变Nd₂Fe₁₄B的室温各向 关键词：     

Nd2(Fe,Si)17合金的结构与磁性

本文对Nd-Fe-Si三元系富铁区域相的结构和磁性进行了研究。结果表明,Nd-Fe-Si三元系富铁区域(Fe>40at％),除出现NdFe₂Si₂三元金属间化合物外(Si>20at％),同时只出现Nd₂(Fe,Si)₁₇赝二元金属间化合物,其中Si取代9d位的Fe原子,而不能形成类似于Nd₂Fe₁₄B的三元金属间化合物,Si取代Nd₂Fe₁₇中的9d位Fe原子后,使晶胞体积缩小;使饱和磁化强度减小;同时使Fe次晶格的铁磁相互作用增强,导致居里温度增高;还使得Fe次晶格的易面各向异性减弱,造成室温下各向异性场减小。 关键词：     

Sm3（F3,Co,Mn）29 compounds：promising materials for permanent magnets

The outstanding hard-magnetic properties are reported of Sm_3Fe_{28.1-x}Co_xMo_{0.9} compounds with x=12, 14, 16. In this alloy system, only a small amount of Mo is needed to stabilize the 3:29 structure so that the magnetic properties are not seriously affected by the presence of this nonmagnetic element. Substitution of Co for Fe leads to a significant increase of the magnetic anisotropy, and for x≥14 the easy magnetization direction changes from easy plane to the easy axis. In this alloy system, the compound Sm_3Fe_{12.1}Co_{16}Mo_{0.9} is a very promising candidate for permanent magnet applications. Its room temperature saturation magnetization (μ_0M_s=1.5 T) and anisotropy field (B_{an}=6.5 T) are comparable to the values for Nd_2Fe_{14}B (μ_0M_s=1.6 T and B_{an}=7 T). However, the Curie temperature of Sm_3Fe_{12.1}Co_{16}Mo_{0.9} is 1020 K, which is appreciably higher than that for Nd_2Fe_{14}B (T_C=588 K).     

永磁性大块金属玻璃Nd60Al10Fe20Co10低温磁性的研究

研究了Nd6 0 Al1 0 Fe2 0 Co1 0 大块金属玻璃磁性随温度的变化关系 ,结果表明Nd6 0 Al1 0 Fe2 0 Co1 0 在室温下表现为永磁性 ,随着温度的降低 ,矫顽力和磁滞回线形状都有很大的变化 .交流磁化率在 18K左右出现尖峰而且峰值温度随频率变化 ,表明该大块非晶体系中存在自旋玻璃态     

铜钨合金高温高压性质的第一性原理研究

采用基于密度泛函理论的第一性原理方法,研究了三种不同比例铜钨合金(Cu3W,Cu W,Cu W3)的基态及高温、高压下的电子结构、弹性性质和热力学性质.弹性常数计算结果表明Cu3W为结构不稳定相,Cu W和Cu W3为结构稳定相,与声子色散曲线得到的结论一致.通过对态密度的分析,发现随压强的增大,金属键键能增大,并且态密度有向深能级移动的趋势.通过准简谐德拜模型和准简谐近似模型分别计算、分析和对比了三种铜钨合金在不同温度和压强下的体弹模量、热膨胀系数、德拜温度和比热容.     

First-principles study of the structural and thermodynamic properties of AsNMg3 antiperovskite

The structural and elastic properties of the antiperovskite semiconductor AsNMg₃ are investigated using the full-potential linearized augmented plane wave plus local orbital (FP-LAPW+lo) method within the generalized gradient in the frame of the density functional theory. The ground state properties such as lattice constant, bulk modulus, pressure derivative of the bulk modulus and elastic constants are in good agreement with numerous experimental and theoretical data. Through the quasi-harmonic Debye model, in which the phononic effects are considered, we have obtained successfully the thermodynamic properties such as the thermal expansion coefficient, Debye temperature and specific heats in the whole pressure range from 0 to 30 GPa and temperature range from 0 to 1200 K.     

Effects of underlayer materials and substrate temperatures on the structural and magnetic properties of Nd2Fe14B films

Thin films of Nd_2Fe_{14}B were fabricated on heated glass substrates by dc magnetron sputtering. Different material underlayers (Ta, Mo, or W) were used to examine the underlayer influence on the structural and magnetic properties of the NdFeB films. Deposited on a Ta buffer layer at 420℃, the 300 nm thick NdFeB films were shown to be isotropic. But when the substrate temperature T_s was elevated to 520℃, the Nd_2Fe_{14}B crystallites of (00l) plane were epitaxially grown on Ta (110) underlayer. In contrast, Mo (110) buffer layer could not induce any preferential orientation in NdFeB film irrespective of the substrate temperature or film thickness. The W buffer layer was found to be most effective for the nucleation of Nd_2Fe_{14}B crystallites with c-axis alignment perpendicular to the film plane when T_s<490℃. But at T_s=490℃ the magnetic layer became isotropic. The maximum coercivity obtained was about 995 kA/m for the 100nm film deposited on W underlayer at 490℃. These variations were tentatively explained in terms of the lattice misfit between the underlayer and the magnetic layer, combined with the considerations of underlayer morphologies.     

Low temperature specific heat and thermal conductivity of bulk metallic glass (Cu50Zr50)94Al6

The low temperature specific heat and thermal conductivity of (Cu₅₀Zr₅₀)₉₄Al₆ bulk metallic glass have been studied experimentally. A low temperature anomaly in the specific heat is observed in this alloy. It is also found that in addition to Debye oscillators, the localized vibration modes whose vibration density of state has a Gaussian distribution should be considered to explain the low temperature phonon specific heat anomaly. The phonon thermal conductivity dependence on temperature for the sample does not show apparent plateau characteristics as other glass materials do; however, the influence of the resonant scattering from the localized modes on the lattice thermal conductivity is prominent in the bulk metallic glass at low temperatures.     

Elasticity and thermodynamic properties of RuB2 under pressure

First-principles calculations of the crystal structure and the elastic properties of RuB₂ have been carried out with the plane-wave pseudopotential density functional theory method. The calculated values are in very good agreement with experimental data as well as with some of the existing model calculations. The elastic constants c_ij, the aggregate elastic moduli (B, G, E), Poisson's ratio, and the elastic anisotropy with pressure have been investigated. Through the quasi-harmonic Debye model considering the phonon effects, the isothermal bulk modulus, the thermal expansions, Grüneisen parameters, and Debye temperatures depending on the temperature and pressure are obtained in the whole pressure range from 0 to 60 GPa and temperature range from 0 to 1100 K as well as compared to available data.     

Er3(Fe,Co, M)29化合物(M=Cr,V, Ti,Mn, Ga,Nb)的结构与磁性

合成了Er_３Fe_29-x-yCo_xM_y化合物(M=Cr, V, Ti, Mn, Ga, Nb )并用x射线衍射和磁测量等手段研究了它们的结构和磁性. 发现Fe基Er_３(Fe,M)_２９化合物结晶成哑铃对Fe-Fe无序替代的Th₂Ni₁₇型结构(P6₃/mmc空间群)而不能形成Nd₃(Fe,Ti)_２９型结构，因此其化学式也可以用Er_2－n(Fe,M)_17+2n (n=0.2)表示. 当Er_３Fe₂₉化合物中部分Fe原子被M原子所取代时，其居里温度均有一定程度的提高. 所有Er_３(Fe,M)_２９化合物在室温均为易面型各向异性. 当Er_３(Fe,M)_２９ (M=Cr, V)中的部分Fe原子被Co原子取代且Co原子数与Fe原子数达到一定比值时，得到一个单斜结构的新相. 磁测量表明Er_３Fe_19.5Co₆V_3.5在室温可能为单轴各向异性，在162K出现自旋重取向，其各向异性由易轴型变为易面型. 在5K下于难磁化方向磁化时观察到一个一级磁化过程(FOMP). 关键词： 稀土金属间化合物 晶体结构 磁晶各向异性     

Electronic and thermal properties of B2-type AlRE intermetallic compounds: A first principles study

The ground state electronic structure and thermal properties of B₂-type intermetallic compounds AlRE (RE: Pm, Sm, Eu, Tb, Gd and Dy) have been studied using a self-consistent tight-binding linear muffin-tin orbital (TB-LMTO) method at ambient as well as at high pressure. These compounds show metallic behavior under ambient condition. The band structure, total energy, density of states and ground state properties like lattice parameter, bulk modulus are calculated in the present work. The Debye-Grüneisen model is used to calculate the Debye temperature and the Grüneisen constant. The calculated results are in good agreement with the reported experimental and other theoretical results. The variation in the Debye temperature with pressure has also been reported. We present a detailed analysis of the role of f electrons of RE in the AlRE system.