介观结构对纳米晶软磁合金巨磁阻抗效应影响的理论分析

根据用原子力显微镜对Fe基纳米晶Fe_73.5Cu₁Nb₃Si_13.5B₉合金薄带的介观结构和巨磁阻抗效应的实验研究结果，提出了纳米晶软磁合金巨磁阻抗效应受其介观结构影响的理论模型.该模型成功地解释了低频对纳米晶软磁合金巨磁阻抗效应的影响，反映了现有“三明治”理论的主要特征，并弥补了它的不足；同时指出了纳米晶粒电导率σ、磁导率μ对合金巨磁阻抗效应有影响. 关键词： 铁基纳米晶合金 介观结构 巨磁阻抗效应 介观模型     

多层膜［Co85Cr15/Pt］20的磁性、垂直磁记录特性和微结构的关系

采用磁控溅射法制备了性能优良的以Pt为缓冲层的［Co85₈₅Cr15_{15/Pt］2020 多层膜，研究了溅射气压对［Co8585Cr1515/Pt］2020多层膜微结构和磁性的 影响.研究结果表明，Ar溅射气压对［Co8585Cr1515/Pt］2020多层膜的微结构 、垂直磁各向异性和矫顽力有重要的影响 关键词： 溅射气压 多层膜 垂直磁各向异性 有效磁各向异性常数}     

新型金属间化合物Sm(TiFe)12的结构与磁性

SmTiFe_x(x的数值为8—11)可形成稳定的金属间化合物,经测定,晶体结构属于ThMn₁₂型四方结构,空间群为14/mmm,本文着重分析了Sm(TiFe)₁₂和Gd(TiFe)₁₂的结构和磁性。Sm(TiFe)₁₂具有很强的单轴磁晶各向异性,易磁化方向为c轴,居里温度610K。通过对Gd(TiFe)₁₂磁性的研究,进一步分析了在Sm(TiFe)₁₂中Sm和Fe次晶格的各向异性,实验结果表明,Sm和Fe次晶格都具有单轴磁晶各向异性,易磁化方向皆沿c轴。这是继Nd₂Fe₁₄B型永磁体以后发现的又一种具有单轴磁晶各向异性的三元稀土-铁金属间化合物。 关键词：     

Fe15.38Co61.52Cu0.6Nb2.5Si11B9纳米晶软磁合金的交流磁性

研究了退火温度对Fe_15.38Co_61.52Cu_0.6Nb_2.5Si₁₁B₉纳米晶软磁合金交流磁性的影响,并且分析了获得较好软磁性能的可能原因.合金的电阻率随着退火温度的增加逐渐降低.μ'f0值与饱和磁化强度M_s之间没有明显的正比关系,合金的旋磁比γ随退火温度的升高应呈不规则的 关键词： 纳米晶合金 软磁材料 品质因数 热处理     

NdFe10M2(M=Mo,Cr)渗C(N)化合物的结构和内禀磁性研究

本文采用气—固反应，将Ｃ、Ｎ原子渗入到ＮｄＦｅ₁₀Ｍ₂结构中的间隙位，不改变它们的ＴｈＭｎ₁₂型结构，进而研究了ＮｄＦｅ₁₀Ｍ_xZ_x（ｚ＝Ｃ，Ｎ）的内禀磁性，Ｃ，Ｎ原子对它们的磁性影响不尽相同，其中ＮｄＦｅ₁₀Ｍｏ₂Ｃ_0.8有单轴各向异性，磁晶各向异性场Ｈ_s＝１１６．０ｋＯｅ。最后对样品进行了穆斯堡尔谱测量，研究了它们的超精细场特性。 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     

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     

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     

各向同性纳米结构Fe-Pt薄膜的结构和磁性

采用直流溅射和热处理技术制备了两个各向同性的纳米结构Fe-Pt永磁合金薄膜系列,并研究了它们的结构和磁性.研究表明,在富Fe双相纳米结构Fe-Pt永磁合金薄膜中,仅由硬磁的FePt相与软磁的Fe₃Pt相组成;在同一系列中,随Fe层厚度的增加,饱和磁极化强度和剩磁明显增大.由Kelly-Henkel图研究指出,在上述Fe-Pt纳米结构永磁合金薄膜中,磁相互作用主要由近邻纳米晶粒间的铁磁交换相互作用控制. 关键词： 磁性薄膜 纳米结构 矫顽力     

Fe-Cu-Nb-Si-B纳米晶体软磁材料中有效磁各向异性的测定

研究了成分为Fe_73.5Cu₁Nb₃Si_13.5B₉的纳米晶体结构的软磁材料的磁各向异性。理论分析及测量结果说明,用趋近饱和的磁化过程可以测定出这种材料中的有效磁各向异性常数,它比晶粒中的磁晶各向异性常数K₁约小一个数量级。 关键词：     

纳米超微晶Fe73.5Cu1Mo3Si13.5B9合金显微结构和磁性的研究

对纳米晶Fe_73.5Cu₁Mo₃Si_13.5B₉合金的原始制备态和各退火态样品进行了室温Mossbauer谱研究,结果表明晶化态的合金存在α-Fe(Si)微晶相和晶界的非晶相。晶相和非晶相内场和面积随退火温度的变化是退火时Cu,Mo,B等成分的扩散和在各相中的再分配引起的。最佳磁性能对应非晶相中的铁量占合金铁总量的30％左右,超微晶合金的双相无规各向异性模型表明,一定量的非晶相对保持纳米晶优异的软 关键词：     

Studies of thin FeAlN films prepared by different techniques

The microstructure, morphology, and magnetic properties of FeAlN films deposited by reactive rf magnetron sputtering with subsequent treatment by three techniques, namely, in situ, ex situ (with the sputtering and annealing processes separated), and thermal crystallization of amorphous alloys, have been studied. FeAlN films prepared by the ex situ technique exhibit the best soft magnetic characteristics. Thermal crystallization of amorphous alloys produced films with properties having the highest thermal stability. Films 800-to 1000-nm thick were found to have the best soft magnetic properties. The dependences of the properties of FeAlN films on nitrogen content and annealing temperature were established. The conditions favoring the preparation of thin nanostructured FeAlN films featuring the best soft magnetic characteristics (saturation induction B _S = 1.8 T, coercivity H _C = 1.2 Oe, magnetic susceptibility μ₁ (1 MHz) = 3400) were determined.     

Role of Ag addition in L10 ordering of FePt-based nanocomposite magnets

The FePt system has important perspectives as high-temperature corrosion-resistant magnets. In the form of rapidly solidified melt-spun ribbons, FePt-based magnets may exhibit in certain cases a two-phase hard–soft magnetic behaviour. The present paper deals with a microstructural and magnetic study of FePtAgB alloys with increasing Ag content. The aim is to identify and confirm the effect of Ag addition in decreasing the temperature of the FePt disorder–order structural phase transformation. A detailed high-resolution transmission electron microscopy study is employed, and the alternative disposal of hard and soft regions within the two-phase microstructure is observed and interpreted with respect to the X-ray diffraction results. In the as-cast Ag-containing samples, it is shown that there is an optimum of the Ag content for which best magnetic properties are obtained. Ag addition creates a nonlinear behaviour of the coercive field and the ordering parameter, similar to the RKKY interaction-induced interlayer exchange coupling (IEC) observed in magnetic layers separated by non-magnetic spacer layers. Direct formation of the L1₀ phase from the as-cast state in the FePtAgB alloys is reported with magnetic parameters compatible to other exchange spring permanent nanomagnets. These findings open novel perspectives into utilization of such alloys in applications requiring magnets operating in high-temperature industrial environments.     

Inverted near-surface hysteresis loops in heterogeneous (nanocrystalline/amorphous) Fe<Subscript>81</Subscript>Nb<Subscript>7</Subscript>B<Subscript>12</Subscript> alloys

Inverted hysteresis loops were observed for the first time in the near-surface layers of heterogeneous (nanocrystalline/amorphous) Fe₈₁Nb₇B₁₂ alloys. In particular, a negative residual magnetization is observed when a positive magnetic field applied in the sample plane is decreased to zero. The inverted hysteresis is qualitatively explained within the framework of a two-phase model, according to which the heterogeneous alloys contain two dissimilar phases exhibiting uniaxial magnetic anisotropy and featuring antiferromagnetic exchange interaction.     

在钴基非晶合金中用过渡元素取代硼对感生磁各向异性的影响

研究了用少量V和Nb代替钴基非晶合金中的B对感生磁各向异性的影响。用圆片形的试样在260—320℃进行等温磁场退火,用一灵敏的磁转矩仪测定了形成感生磁各向异性的动力学曲线。设弛豫时间服从对数正态分布,计算了动力学参数。结果说明,用V或Nb在钴基非晶合金中取代B可以有效地降低K_u的饱和值,但对动力学参数影响很小。讨论了添加少量过渡元素对感生磁各向异性以及磁性稳定性的影响问题。 关键词：     

Grain growth process of two-phase nanocrystalline soft magnetic materials

In order to clarify the origin of the high thermal stability of the microstructure in bcc-Fe/amorphous two-phase nanocrystalline soft magnetic materials, we have investigated the changes in the magnetic and microstructural properties upon isothermal annealing at 898 K for an Fe₈₉Zr₇B₃Cu₁ alloy by means of transmission electron microscopy, Mössbauer spectroscopy and DC magnetometry. The mean grain size was found to remain almost unchanged at the early stage of annealing. However, rapid grain coarsening was evident at an annealing time of 7.2 ks where the intergranular amorphous phase begins to crystallize into Fe₂₃Zr₆. The grain growth process with a kinetic exponent of 1.6 is observed for the growth process beyond this annealing time, reflecting the disappearance of the intergranular amorphous phase. Our results confirm that the thermal stability of the bcc-Fe/amorphous two-phase nanocrystalline soft magnetic alloys is governed by the residual amorphous phase.     

氢对几种非晶态合金磁性的影响

本文研究了电解充氢对3种不同成分的非晶态合金磁性的影响。实验结果表明,充氢后试样变得很脆,软磁特性显著变劣,但饱和磁化强度σ₃和平均超精细场H_f显著提高。将试样在室温下放置,随着氢气的外逸,磁性、韧性以及H_f可得到逐步恢复。 关键词：     

Investigation of the magnetic properties and magnetic structure parameters of nanocrystalline Fe<Subscript>79</Subscript>Zr<Subscript>10</Subscript>N<Subscript>11</Subscript> films

The magnetic properties (magnetization curve, ferromagnetic resonance spectrum) of nanocrystalline Fe₇₉Zr₁₀N₁₁ films obtained by RF magnetron sputtering with subsequent annealing were studied experimentally, along with the fundamental magnetic constants of these films (saturation magnetization M _S, local magnetic anisotropy energy K, and the exchange coupling constant A). The magnetic properties are discussed within the random magnetic model, which determines the correlation of the magnetic properties with the fundamental magnetic constants and nanostructure parameters (grain size, magnetic anisotropy, and correlation radius R _C). The exchange correlation length 2R _L for the film magnetic microstructure was determined by correlation magnetometry.     

Dependence of Magnetic Properties on Composition of Nanocrystalline Fe–M–B–Cu (M: Zr,Nb, Mo,Ti, Ta) Alloys

The specialized rf-Mössbauer technique is used to elucidate the magnetic properties of NANOPERM-type nanocrystalline alloys. The influence of alloy composition on the soft magnetic properties is studied for the Fe₈₀M₇B₁₂Cu₁ (M: Ti, Ta, Nb, Mo, Zr) alloys. The rf-Mössbauer experiments allowed us to distinguish magnetically soft nanoclusters from magnetically harder microcrystalline phases. The measurements performed as a function of the rf field intensity allowed the determination of the distribution of anisotropy fields related to the size distribution of bcc nanoclusters. Smaller anisotropy fields in the nanocrystalline phase were found in Nb-, Zr-, and Mo-containing alloys as compared with the alloys which contain Ti and Ta. The Mössbauer measurements were supplemented by X-ray diffraction determination of the size of nanocrystalline grains.