七种非晶铁磁合金的体积磁致伸缩研究

 强制体积磁致伸缩的数量级极小（10^-10~10^-9[(10³/4π)(A/m)]^-1），如通过测量三个互成直角方向的线磁致伸缩（10^-6[(10³/4π)(A/m)]^-1）再正负迭加则很难测准。本文利用热力学关系：(dω/dH)_T,p=-(dM_s/dp)_T,H，用静水压法在0.000 1~2.4 GPa范围测得七种非晶合金Fe_81.6Si_4.6B_13.8、Fe_46.3Co_0.03Ni_46.5Si_3.75V_0.92B_2.5、Fe₇₅Cr₅Si₅B₁₅、Fe_73.9Co_8.3Si_4.4B_13.4、Fe₇₅Ni₅Si₅B₁₅、Fe_78.75Cu_1.25Si₅B₁₅和(Fe_0.85Co_0.15)₈₂Cu_0.4Si_4.4B_13.2的强制体积磁致伸缩及其随静水压p的变化。结果表明：（1）其中六种属于第一类压磁效应。(dω/dH)_T,p在大部分压力下为正，p增加时M_s不断减小；(dω/dH)_T,p仅在几个狭窄的压力范围为负。可归因于磁性原子与非磁性原子的化学短程序在压力下的变化。（2）非晶合金Fe_78.75Cu_1.25Si₅B₁₅属于第二类压磁效应。(dω/dH)_T,p在绝大部分压力下为负。M_s反常升高与Cu的特殊作用有关。     

静高压下非晶(Fe0.99,Mo0.01)78Si9B13合金晶化过程的热力学研究

 在600~930 K，常压到7 GPa的范围内，对非晶(Fe_0.99,Mo_0.01)₇₈Si₉B₁₃合金等温等压退火30 min。实验表明：其晶化产物α-Fe(Mo, Si)、Fe₃B和Fe₂B相的析出与所加压力密切相关。压力使非晶(Fe_0.99,Mo_0.01)₇₈Si₉B₁₃合金的晶化温度和亚稳Fe₃B相的析出温度下降，在一定的压力和温度下，亚稳Fe₃B相将向稳定Fe₂B相转变，其转变温度随压力而变化。还对非晶(Fe_0.99,Mo_0.01)₇₈Si₉B₁₃合金的晶化和亚稳Fe₃B到稳定Fe₂B转变的热力学机制进行了讨论，并给出Fe₃B向Fe₂B的相转变方程。     

150keV Ar离子辐照非晶态合金表面发泡和溅射形貌研究

150keV Ar离子辐照非晶态合金Fe₃₉Ni₃₉Mo₂Si₁₂B₈、Fe₄₀Ni₄₀Si₁₂B₈、Fe₃₉Ni₃₉V₂Si₁₂B₈、Fe₇₇Cr₂Si₅B₁₆和Fe₇₈Si₁₀B₁₂,用扫描电子显微镜(SEM)观测研究了表面损伤形貌剂量变化的过程.低剂量时表面发泡形成.发泡随剂量增加受到溅射腐蚀,表面形成坑洞或针孔,针孔密度随剂量增加而增加,高剂量时,表面损伤以溅射为主,溅射对表面的腐蚀导致多孔粗糙的表面损伤结构建立,并且这些结构与靶材料有着密切的关系.     

Y对Fe-Si-B 合金非晶形成能力及软磁性能的影响

本文通过铜模吸铸法和单辊甩带法分别制备出一系列楔形试样和非晶条带试样, 系统研究了稀土金属Y对Fe₇₈Si₉B₁₃合金非晶形成能力及其软磁性能的影响. 结果表明, 少量Y取代 Fe-Si-B 非晶合金中的Fe 可大大提高该合金的非晶形成能力并促进过冷液相区的产生. 当Y含量为3 at.%时, 合金具有最大的非晶形成能力, 其临界厚度为313 μm, 相应的非晶过冷液相区宽度达到65 K. 该系列非晶合金具有优良的软磁性能, 其矫顽力(H_c)均低于200 A/m, Y含量为1 at.%时, 饱和磁感应强度(B_s) 达到最大值1.67 T.     

Fe78B13Si9、(Fe0.99Mo0.01)78B13Si9非晶合金的激波晶化实验研究

 研究了Fe₇₈B₁₃Si₉、(Fe_0.99Mo_0.01)₇₈B₁₃Si₉非晶合金的激波晶化行为。激波是由氢-氧爆炸产生的。实验结果表明：激波能使非晶合金在微秒时间内晶化,晶化主相为α-Fe基固溶体,次晶化相为Fe₃Si,且观察到α-Fe基因溶体晶格常数变小。用DTA分析进一步证实：激波晶化是比较完全的,晶化相相当稳定。     

Mn掺杂对Nd-Fe-B纳米复合永磁合金结构的影响

利用XRD和XAFS技术研究了淬火速度为20m/s的退火和未退火Nd₉Fe_85－xB₆Mn_x(x=0.5,1.0)样品的长程序结构和局域结构.结果表明:初始制备样品,微量Mn原子的掺杂有利于纳米复合Nd-Fe-B磁性材料中Nd₂Fe₁₄B硬磁相和α-Fe软磁相的结晶度增加,而随着Mn掺杂量的增加,Fe原子周围配位有序度升高;退火后,掺杂微量的Mn元素并没有进一步提高Nd₉Fe_85－xB₆Mn_x样品的结晶度,也没有生成新的物相.本文提出,在快淬制备过程中,微量的Mn原子进入纳米复合Nd-Fe-B磁性材料的磁体主相形成亚稳相;退火处理后,Mn原子退出初始的磁体主相而进入颗粒的晶界.     

Fe40Ni40P12B8非晶合金的冲击晶化实验研究

 本文研究了Fe₄₀Ni₄₀P₁₂B₈非晶合金冲击波加载下的晶化行为，冲击波由二级轻气炮发射的告诉弹丸撞击靶产生。实验结果表明：Fe₄₀Ni₄₀P₁₂B₈非晶合金在冲击波加载下，晶化可在加载时间（微秒量级）内发生；晶化的阈值压力在30~50 GPa之间，相应的冲击温度约为510~800 K，晶化析出相与冲击压力有关，低压下析出相是面心立方γ-(Fe, Ni)固溶体和Fe₃(P_0.37B_0.63)化合物，高压下（大于60 GPa）析出相除了面心立方γ-(Fe, Ni)固溶体和Fe₃(P_0.37B_0.63)化合物之外，还包括(Fe, Ni)₃P化合物。     

EXAFS STUDY OF THE LOCAL STRUCTURE NANOCRYSTALLINE FeZrB(Cu) SOFT MAGNETIC ALLOYS

The changes of local structures around Fe and Zr atoms in the nanocrystalline films of Fe₈₅Zr₉B₆ and Fe₈₄Zr₉B₆ Cu₁ alloys during annealing process were investigated by extended X-ray absorption fine structure (EXAFS) technique. It is confirmed that Zr atoms always exist in amorphous phase and do not dissolve in the bcc α-Fe crystalline phase. The addition of 1 at% Cu lowers the crystallization temperature.     

添加Dy在快淬NdFeB永磁体中的作用

在之前研究Nb元素的添加对快淬(Nd,Dy)_11.5Fe_82.4-mNb_mB_6.1永磁体磁性能、温度特性及显微组织影响的基础上，进一步研究了Dy元素在Nd_11.5-nDy_nFe_81.4Nb₁B_6.1 (n＝0,0.5,1,1.5,2)永磁体中     

Heusler合金Fe2CrGa的磁性与结构

采用KKR-CPA-LDA方法研究了不同混乱占位时Fe₂CrGa合金基态的电子结构和磁结构. 基态能量表明Fe₂CrGa合金更倾向于形成Hg₂CuTi型有序结构,而不是L2₁结构. 能态密度(DOS)分析进一步揭示受晶体场影响的磁性原子内部交换作用是使Fe₂CrGa合金形成 Hg₂CuTi型有序结构的主要原因.测量了不同热处理所得Fe₂CrGa合金的居里温度和分子磁矩, 发现原子占位有序化可以在137K温度范围内调控合金的居里温度.分子磁矩随有序化占位也有相应变化, 分布在2.28μ_B/f.u.—2.48μ_B/f.u.之间.理论计算和实验对比可证明Fe₂CrGa合金是Hg₂CuTi型Heusler合金.     

非晶铁基合金中两类不同的压磁效应

 本文详细介绍了在0.000 1~2.3 GPa流体静压力下测量三种非晶合金饱和磁感应强度B_s和最大磁导率μ_max的实验方法。实验结果表明：三种非晶合金受压后B_s和μ_max表现各异，可归为两大类。（1）第一类压磁效应：总趋势是B_s和μ_max都随压力增加而下降，但在几个压力区B_s反常增高。如Fe₇₅Ni₅Si₅B₁₅非晶合金B_s随压力增加均匀下降，(Fe_0.85Co_0.15)Cu_0.4Si_4.4B_13.2非晶合金的B_s随压力增加降—升—再降。（2）第二类压磁效应，如Fe_78.75Cu_1.25Si₅B₁₅非晶合金的B_s和μ_max随压力增加都有未见报导过的微弱升高。分别结合局域电子模型的交换作用理论和巡游电子模型的刚带理论进行了讨论。     

FORMATION AND MAGNETIC PROPERTIES OF NEW COMPOUNDS R3Fe29-xCrx(R=Y,Ce,Nd,Sm,Gd,Tb,and Dy)

A systematic investigation of structure and magnetic properties of the new R₃Fe_29-xCr_x compounds(R=Y,Ce,Nd,Sm,Gd, Tb,and Dy)has been performed. The Curie temperature of R₃Fe_29-xCr_x increased with increasing atomic number fromR=Ce to Gd and de creased from Gd to Dy. The saturation magnetization of R₃Fe_29-xCr_x at 4.2 K decreased gradually with increasing atomic number from R=Y to Dy,except for Ce. The spin reorientations of the easy magnetization d irection were observed at around 230 K for Nd₃Fe_24.5Cr_4.5 and 180 K for Tb₃Fe_28.0Cr_1.0,and the magnetohistory effects were obser ved for Nd₃Fe_24.5Cr_4.5 and Sm₃Fe_24.0Cr_5.0 in a low field of about 0.04 T. First order magnetization process occurs in magnetic field of around 2.3 T at room temperature for Tb₃Fe_28.0Cr_1.0. The saturation magnetization of Y₃Fe_27.2Cr_1.8 at 4.2 K is 52.2μ_B/f.u., which corresponds to an average magnetic moment of 1.92μ_B per each Fe atom.     

A method based on magnetic moment measurement to identify the structural transition of quenched Fe1 -xGax (x = 0.15ben 0.30) alloys

A method based on the measurement of Fe average atomic magnetic moment to identify the structural transition caused by the increase of Ga content in quenched Fe_{1 - x}Ga_x alloys (0.15 ≤ x ≤ 0.30) is proposed. The quenched Fe_{1 - x}Ga_x alloys show a change of the Fe average atomic magnetic moment from 2.25 μ_B to 1.78 μ_B and then to 1.58 μ_B, which corresponds to the structural transition from A2 to D0₃ and then to B2. The relationship between the structure and the magnetostriction is clarified, and the maximum magnetostriction appears in the A2 phase. The variation tendency of the magnetostriction is well characterized, which also reflects the structural transition.     

Crystal field analysis of the magnetization curves of R2Fe17 and R2Fe17H3 (R=Tb,Ho,Er)

In this paper the values of the crystalline-electric-field parameters A_nm for R₂Fe₁₇ and R₂Fe₁₇H₃ (R=Tb,Ho,Er) are evaluated by fitting calculations to the magnetization curves measured on the single crystal at several temperatures. The fitted A_nm for R₂Fe₁₇ are strikingly different from those for the corresponding R₂Fe₁₇H₃. The energy gaps between the lowest four energy levels for Ho ions in Ho₂Fe₁₇₂ can be reproduced by using the fitted A_nm and exchange field 2μ_BH_ex, which estimated from the fit of the temperature dependence of the spontaneous magnetization combined with inelastic neutron scattering experiment.     

液Zn对Fe2Al5涂层侵蚀的相变过程研究

本文对Fe₂Al₅涂层在液态Zn中的侵蚀相变过程进行了研究,实验结果表明：在侵蚀初期,靠界面张力平衡的作用,先发生热侵蚀,在试样表面形成热蚀沟,当热蚀沟达到一定程度后, 液Zn与Fe₂Al₅相由不浸润变为浸润;同时Zn原子扩散进入Fe₂Al₅相并形成Fe₂Al₅-Zn_x固溶体相(η相);随着侵蚀时间的增加,发生在腐蚀界面上的液Zn对Fe₂Al₅涂层的侵蚀过程是恒温相变过程,相变过程使Fe₂Al₅涂层发生定向熔化. 相变的驱动力来自于相成分的改变所引起的各相自由能的变化及各相间的相平衡的重新建立.     

THE INFLUENCE OF Co SUBSTITUTION ON THE MAGNETIC PROPERTIES AND THE GIANT MAGNETO-IMPEDANCE EFFECT OF (Fe1-xCox)84Zr3.5Nb3.5B8Cu1

The microstructure, magnetic properties and the giant magneto-impedance (GMI) effect of the nanocrystalline (Fe_1-xCo_x)₈₄Zr_3.5Nb_3.5B₈Cu₁ ribbons have been studied. With increasing Co concentration, the nanocrystallized grain size and volume fraction of the α-Fe(Co) phase decrease under the same annealing condition, while the coercivity H_c increases from 1.92 A/m at x=0.0 to 30.38 A/m at x=0.8. The effective permeability drops sharply with increasing Co concentration so that the GMI effect goes down. A value of more than 380% for the magneto-impedance(MI) ratio was measured at frequency f=2.5 MHz and the sensitivity can reach 0.9% (A/m)^-1 for Fe₈₄Zr_3.5Nb_3.5B₈Cu₁ ribbon. When x is equal to 0.8, the MI ratio drops to about 30% and the sensitivity only reaches a value of lower than 0.025% (A/m)^-1. The concise analysis in theory is also expounded.     

POSITRON LIFETIME STUDIES OF Y1-xCaxBa2Cu3O7-δ AND Y1-xCaxBa2Cu3-xFexO7-δ

In this paper it is reported that the measurement of the bulk positron lifetime as a function of substitution content x in the temperature range from 70 to 220K was performed in two high-T_c superconducting systems, Y_1-xCa_xBa₂Cu_3-xFe_xO_7-δ and Y_1-xCa_xBa₂Cu₃O_7-δ. It was found that τ_B of both systems decreases significantly with x and the temperature dependence of τ_B is very weak in normal state. In lower temperature region (Tc), a dramatic x-dependent temperature variation of τ_B was observed in the Ca-substituted system: from a decrease of τ_B with decreasing T to an increase of τ_B. With increasing x, the temperature dependence of τ_B remains weak in the Ca- and Fe- substituted systems. Compared with the experimental data of positron lifetime in other substituted systems and the calculation of the positron density distribution, the authors suggest that positron bulk lifetime spectra behaviour can be interpreted by the physical model based on the transfer of electron density between the CuO₂ planes and Cu-O chains. Therefore, the study of positron lifetime spectra provides a useful means to detect the local charge density and to study the correlation between the electronic structure and the high-T_c superconductivity.     

MAGNETIC PROPERTIES OF BALL MILLED FexCu1-x (x=0.4, 0.5) ALLOY

The samples Fe_0.4Cu_0.6 and Fe_0.5Cu_0.5 ball milled for 50 h are investigated by X-ray diffraction, M?ssbauer spectra, as well as magnetic measurement. The experiments show that the structure of the samples is fcc, with lattice constant 0.361 nm and there are fcc Fe-rich phase and fcc Cu-rich phase in the samples. Most of Fe atoms (91%) are in the fcc Fe-rich phase, which is a ferromagnetic phase. The M-H curve at 1.5 K shows the saturation magnetization of the samples are 80.5 emu/g and 101.6 emu/g for Fe_0.4Cu_0.6 and Fe_0.5Cu_0.5 respectively. The average magnetic moment of Fe atoms is deduced to be 2.40 μ_B . Compared with theoretical predication, the Fe atoms in the fcc phase are in high spin state.     

非晶FeMoSiB合金机械晶化的动力学机制

 研究了非晶(Fe_0.99Mo_0.01)₇₈Si₉B₁₃（FMSB）合金的机械晶化过程和机制,并讨论了局域高压的作用。结果表明：非晶FMSB合金的晶化过程及其产物与球磨强度和球磨时间有密切关系,在低能球磨FMSB非晶过程中,晶化相只有α-Fe(Mo,Si)固溶体,而在高能球磨过程中,除了α-Fe(Mo,Si)固溶体结晶相之外,还分别有(Fe,Mo)₃B和Fe₂B相析出。其晶化机制可归因于由碰撞引起的局域高压和局域高温共同作用的结果。实验结果还表明,机械球磨不仅对非晶FMSB的常压热晶化温度有重要影响,而且对其热晶化结果亦有重要影响。     

非晶Fe78Si9B13合金在高压下的晶化

 本文研究了压力对Fe₇₈Si₉B₁₃非晶合金晶化温度的影响。给出了常压及7.5 GPa压力下的时间－温度－相变图。结果指出：晶化温度不仅与压力的大小有关，而且还与热处理的时间因素有关。此外，高压下bcc-Fe(Si)相结晶区域明显变大。