Effect of Pr on the Structure and Magnetic Properties of CoPt Alloys

对PrxCo50-xPt50(x=0,0.2,0.4,0.6,0.8,1.0)合金的显微结构和磁性能进行了研究。X射线衍射结果表明:经1000℃均匀化后合金为单一的面心立方相(fcc),而经675~750℃退火后合金由硬磁相(面心四方结构,fct)和软磁相组成。随着Pr含量增加,fct的(111)衍射峰向高角度偏移,并且c/a增大导致有序度S减小。合金Pr0.4Co49.6Pt50经675°C退火60min后,矫顽力和剩磁比达到最大值。PrxCo50-xPt50(x=0,0.2,0.4,0.6,0.8,1.0)经675°C退火60min的样品,矫顽力随着Pr含量的增加而单调减小,但剩磁比先增大后减小。     

Co含量对熔体快淬Fe_(55-x)Co_xPt_(15)B_(30)合金的组织结构与磁性能的影响

研究了Co含量对熔体快淬Fe_(55-x)Co_xPt_(15)B_(30)(x=0~45,原子分数,%)合金热处理前后的组织结构和磁性能的影响。结果表明,添加Co可提高Fe_(55-x)Co_xPt_(15)B_(30)合金的非晶形成能力,使x=15~45的快淬合金形成非晶态。经适当热处理后,合金中形成了由有序面心四方结构的永磁(Fe,Co)-Pt(L1_0)相和软磁(Fe,Co)2B相及(Fe,Co)B相组成的纳米复相组织,显示出永磁性;添加Co的合金组织得到明显细化,x=15~45合金平均晶粒尺寸均约为18 nm;其中x=15合金具有最佳的永磁性能,磁能积达到94.4 k J/m3。合金的矫顽力随Co含量的增加而增大,在x=30时达到最大值413.7 k A/m后,随Co含量的进一步增加而减小;这是由于不同Co含量使L1_0相的c/a值发生变化而导致其磁晶各向异性变化的结果。     

Pt缓冲层厚度对FePt薄膜合金相转变和磁性能的影响

利用磁控溅射法制备了具有Pt缓冲层的[FePt]50多层膜.通过x射线衍射(XRD)分析和磁性测量研究了不同缓冲层厚度对样品微结构演变和磁性能的影响.结果表明,随着Pt缓冲层厚度(t≤8.6 nm)的增加,薄膜合金的有序化温度明显降低,晶粒尺寸逐渐减小FePt薄膜样品点阵常数c/a的比值逐渐减小,有序度参数S逐渐增大;同时样品的矫顽力也随着缓冲层厚度的增加而增大,在425℃退火的样品,其矫顽力由缓冲层厚度t=0时的398 kA/m增加到t=8.6nm时的523 kA/m(接近无缓冲层样品在500℃退火的值),平均变化率为14.53 kA·m-1/nm,有效地降低了样品的退火温度;与此同时,剩磁比逐渐减小,从0.68减少到0.56.     

Dy0.5Fe60Pt39.5合金的相转变和磁性能

研究了退火时间对Dy0.5Fe60Pt39.5合金结构和磁性能的影响.通过热磁曲线的测量获得了软磁相和硬磁相的居里温度.实验表明:由于退火时间的增长,合金中的短程有序度增加,使无序的面心立方相并不是真正的无序相.合金的矫顽力和剩磁比都是退火时间的函数,最佳的热处理条件是在600 °C退火5 h.根据合金相转变和微结构的变化对磁性能的结果进行了解释.     

Tb0.3Dy0.7(Fe1-xPtx)1.95合金的结构与磁致伸缩特性研究

利用XRD、SEM和电阻应变片等方法研究了Tb0.3Dy0.7(Fe1-xPtx)1.95(x=0.00,0.02,0.04,0.06,0.08)合金的微结构和磁致伸缩特性.结果表明:当Pt含量x≤0.06时,合金为具有立方MgCu2型结构的Laves单相,Pt置换Fe导致合金相的晶格常数α线性增大;磁致伸缩系数λ随Pt含量的增加不断减小,随外磁场(H≤500mT)的增大而单调增大;当合金在950℃退火4 h,可获得较好的磁伸缩性能.在x=0.08时,合金中出现微量第二相Fe3Dy,证实Pt在Tb0.3Dy0.7Fe1.95合金中的最大固溶度小于5at%.     

Fe60.5-xPt39.5Ndx(x≤1.5)合金相转变和居里温度研究

采用X射线衍射,差热分析和居里温度测量等方法研究Fe60.5-x Pt39.5Ndx合金的相转变、居里温度和有序度。结果表明：Nd的添加有利于稳定FCC相结构;随着Nd含量x的增加,Fe60.5-xPt39.5Ndx合金的有序度及有序FCT相的居里温度都逐渐减小     

La（Ni,Sn）x（x=5.0～5.4）无Co贮氢合金的相结构与电化学性能

系统研究了La（Ni,Sn）x（x=5.0～5.4）无Co贮氢合金的化学计量比x对合金相结构和电化学性能的影响.XRD分析表明,除在x=5.4的合金中析出有少量的第二相（Ni）外,其它合金均为单相CaCu5型结构.随着x的增加,合金晶胞的c/a比值逐渐增大,并使合金的吸氢体积膨胀率（△V/V）明显减小,其原因主要与过计量比合金的晶体结构中存在有沿c轴定向排列的Ni-Ni“哑铃”对的结构特征有关.电化学测试表明,增大x会使合金的最大放电容量和高倍率放电性能（HRD）有所降低,但合金的循环稳定性得到显著提高.合金HRD值的减小主要是由于过计量比降低了合金电极的电催化活性,而合金循环稳定性的显著改善则主要归结于过计量比合金较小的吸氢体积膨胀及粉化倾向所致.     

非化学计量比贮氢合金Ml(Ni0.71Co0.15Al0.06Mn0.08)x的电化学性能

研究了化学配比x对贮氢合金Ml(Ni0 .71 Co0 .1 5Al0 .0 6Mn0 .0 8) x(4.6≤x≤ 5.2 )的结构、组织、电化学性能和 p c T特性的影响。结果表明 ,随着x增大非化学计量比合金点阵常数a值减小 ,c值增大 ,单胞体积减小 ,当x =5.2时c/a达到最大值。x =5.0的化学计量比合金具有最小的点阵常数和单胞体积。放电容量、充放电循环稳定性和 p c T曲线平台压均随着x增大而提高 ,当x =5.2时达到最大放电容量和最佳循环稳定性。     

Heusler合金Ni2MnGa磁性微观机理的第一性原理

采用量子力学计算软件包研究了单晶Heusler合金Ni2MnGa的结构参数、磁矩、四方变形以及磁性微观机理,并将计算结果与实验值和其它理论计算值进行了比较.计算所得的结构参数和磁矩相对于局域自旋密度近似值而言,与实验值符合得更好.四方变形中,发现磁矩在c/a=1附近有一个尖锐的最小值,在c/a≈0.94处有一个局域最大值,此磁矩的局域最大值对应着一个稳定的马氏体.总磁矩随c/a的变化主要来自Ni原子:由于一个原胞中有两个Ni原子对其总磁矩作了贡献,因而屏蔽了Mn原子的贡献所致.对总态密度的分析表明,自旋向上的态密度位于费米面以下,而自旋向下的态密度有两个主峰,分别位于费米面两侧,这是磁有序合金的一个典型特性.且合金磁性主要源于Mn原子的d-eg和d-t2g亚带,这与实验结果一致.     

Co-Gd合金在尿素-乙酰胺-NaBr熔体中的电沉积及合金性能

在尿素-乙酰胺-NaBr熔盐中采用电沉积方法制备了Co-Gd合金薄膜.运用循环伏安技术研究了Gd、Co的共沉积行为.通过扫描电子显微镜、X射线能谱仪和X射线衍射仪研究了电流密度对镀层表面形貌、元素组成及镀层结构的影响.研究发现,Gd含量随着电流密度的增加呈先增加后减少的趋势,在电流密度为12.5 mA/cm2时达到最大含量54.97%(质量分数).镀层的表面形貌随着Gd含量的增加而变得粗糙.镀态时镀层结构为非晶态,300 ℃热处理后转化为Co(Fm3m)相,在600 ℃热处理后又出现GdCo5 (P6/mmm)相.采用振动样品磁强计测试了镀层的磁性能.结果表明,镀层中Gd的含量对镀层的磁性能有重要影响.在热处理过程中,镀层的饱和强度在600 ℃热处理时达到最大值550.43 kA/m,而矫顽力则在400 ℃热处理时达到最大值34.97 kA/m.     

Effect of Fe on Microstructure and Coercivity of SmCo-Based MagnetsEI北大核心CSCD

High-temperature permanent magnets have an important application in the aerospace and other high-tech fields, among which 2:17-type SmCo magnets have become the first choice for high-temperature permanent magnets due to the strong magnetic anisotropy and high Curie temperature. Although there are studies on the effect of Fe on the remanence and coercivity, the role that Fe plays on coercivity mechanism of SmCo magnets is still unclear. In this work, Sm(CobalFexCu0.08-0.10Zr0.03-0.033) z (x= 0.10-0.16, z=6.90 and 7.40) magnets are prepared and the magnetic properties under different temperatures are investigated. The magnets with an intrinsic coercivity of 603.99 kA/m and a maximum energy product of 87.30 kJ/m(3) at 500 degrees C. are obtained. It is revealed that at room temperature the coercivity of the magnets increases with increasing Fe content, however, at 500 degrees C. the coercivity shows an opposite dependency on Fe content. Moreover, the effect of Fe on coercivity is more obvious at low z value. The phase structure and composition analyses were characterized by XRD and TEM. The results show that with the increase of Fe content, the size of the 2: 17R cell phase increases, the volume ratio of cell boundary 1: 5H phase decreases, and furthermore, both Fe content in the 2: 17R phase and Cu content in the 1: 5H phase increase. The variations of Fe and Cu contents in both phases lead to the change of the domain wall energy difference. With the increase of Cu content of 1:5H phase, the domain wall energy of 1: 5H phase (gamma(1:6)) drops faster at room temperature, the coercivity is determined by gamma(2:17)-gamma(1:5), so the coercivity increases with increasing Fe content. While at 500 degrees C, due to gamma(1:6) at its Curie temperature, the coercivity is mainly determined by the domain wall energy of 2: 17R phase (gamma(1:17)), which decreases with increasing Fe content. The increase of Fe content at the low z value results in a smaller growth of cell size, which leads to a more significant change in coercivity.     

MAGNETIC PROPERTIES OF Nd_2(Fe_(1-x)M_x)_(14)B(M=C,Si)ALLOYS

The magnetic properties of Nd_2(Fe_(1-x)M_x)_(14)B(M=C and Si) compounds have been investi-gated.Substituting Fe by small amount of metalloid C and Si atoms,the compounds are intetragonal structure and have uniaxial anisotropy.The substitution of C for part of Fe de-creases the Curie temperature of the compounds and the intrinsic coercivity of bond samples atlow temperature.The replacement of Fe by Si makes the Curie temperature increase with amaximum at the vicinity of x=0.15.When the range of the content of Si is 0≤x≤0.10,thecoercivity distinctly increases at room temperature.from 62.7 kA/m at x=0 to138.7kA/m at x=0.06,where the residual magnetization has a maximum:in the mean timethe saturation magnetization decreases only by a small amount.     

添加Si对HDDR各向异性Nd-Fe-Co-B-Si系永磁磁粉的磁性能与磁粉结构的影响

本文研究了添加微量元素Si对HDDR工艺制备各向异性Nd-Fe-CO-B-Si系永磁磁粉的磁性能和磁粉结构的影响。研究结果表明：添加Si可以显著地提高磁粉的矫顽力和各向异性，Si的添加可以细化晶粒，还能使反磁化畴难以形核，因而磁粉的矫顽力较高。目前对于添加Si的Nd-Fe-B系化合物各向异性的机制有两种解释。     

Nb含量对NdFeB合金HDDR工艺及显微组织的影响

探讨了Ｎｄ含量对纯三元ＮｄＦｅＢ合金氢化／歧化／脱氢／重组（ＨＤＤＲ）工艺以及其显微组织变化的影响。结果表明：Ｎｄ含量的增加促进了ＨＤＤＲ工艺过程加快、最佳工艺处理温度降低,并使其显微组织中晶粒尺寸的不均匀性增大。     

Effects of Pr on the structure and magnetic properties of FePt alloys

The effects of Pr on the structure and magnetic properties of PrxFe60.5-xPt39.5 alloys （x = 0, 0.5, 1.0, and 1.5） were investigated. X-ray diffraction data indicated that the phase transition temperature of FePt based alloys from disordered face-centered-cubic to ordered face-centered-tetragonal cubic decreases with the increase in Pr concentration. Pr plays the role of a grain refiner and it can enhance the exchange coupling between soft magnetic phase and hard magnetic phase. The results indicate that the replacement of Fe by Pr can significantly improve the remanence and coercivity of the Fe60.5Pt39.5 alloy. These results can be explained on the basis of phase transformation and microstructure. Both the remanence ratio and coercivity of the FePt based alloy as a function of the Pr content are increased by the optimum addition of 0.5 at.% Pr.     

MnBi合金的结构与永磁性能

本文综述了有关MnBi低温相永磁材料方面的最新研究进展，对MnBi永磁合金的制备方法、结构及其永磁性能作了较为详尽的介绍。快淬和高能球磨方法可望成为单相性好的MnBi永磁合金的实用制备工艺。合金化方面的研究也显示出MnBi系合金的潜力。MnBi合金有望成为永磁性能较好且有好的温度特性(尤其是在高温时有很高的矫顽力并有正的矫顽力温度系数)的材料。MnBi合金可作为特殊用途的永磁材料，在许多领域获得应用。     

Preparation of cobalt-modified magnetite and its magnetic properties

Magnetite was modified by reaction with alkaline solution containing Co^2 and Fe^2 to obtain a cobalt ferrite layer on the surface of particles. The influences of modification conditions on the properties were investigated. The as-prepared particles were characterized by X-ray diffraction(XRD) and transmission electron microscope(TEM). The results show that pH value influences the particles composition directly, the desirable CoFe2O4 is obtained as pH value is 12. The coercivity of particles increases with the increase of cobalt content, and the cobalt efficiency reaches a maximum value at cobalt content of 2.71% (mass fraction). With cobalt modification, the magnetite particles have the similar lattice constant and structure to that without cobalt modification, and the squareness ratio is almost 0.5. The increase of the coercivity is attributed to the uniaxial magnetic anisotropy and magnetocrystalline anisotropy of cobalt-ferrite itself.     

Effects of ZrO2 on the structure and magnetic properties of CoPt thin films

[CoPt 1.5 ml/ZrO2 xnm]10 multilayer films were deposited on glass substrates by magnetron sputtering and then annealed in vacuum at 600℃ for 30 min. Their structures and magnetic properties were investigated as a function of ZrO2 content. The results show that the grain size and coercivity first increase and then decrease with the increase in ZrO2 content. The maximum coercivity and grain size are obtained at 37 vol.% of ZrO2. The content of ZrO2 in the film plays an important role in the separation of CoPt grains and in the reduction of intergrain exchange interaction. On the basis of the studies of angular dependent coercivity, it is found that the magnetization reversal of CoPt films with （111 ） texture is different from either the domain wall motion or the S-W type of rotation mode.     

钛掺杂无氢类金刚石薄膜疏水性能研究

利用X射线衍射分析（XRD）和BH测试仪分别研究了元素Tb、Zr的添加对HD法制备NdFeB永磁体的微结构及磁性能的影响规律。微结构研究表明,元素Tb、Zr添加前后的磁体都主要由四方相Nd2Fe14B（P42/mnm）和微量的富Nd相构成;但Tb和Zr的添加明显改变了永磁体的取向特性和磁性能;采用HORTA法计算表明,Tb和Zr的添加虽然都使永磁体的（004）、（006）、（008）极密度因子减小,但是室温下磁性能测试表明,Zr的添加降低了磁体的矫顽力,而Tb添加后永磁体的矫顽力有了明显的提升,从2038 kA/m提升到2302 kA/m;Kronmüller-Plot关系曲线表明,3种合金的矫顽力机理均为磁畴成核反转机制。     

Elemental segregation in Co-Cr-P-Pt/Cr magnetic thin films by Imaging Filter

The microstructure and magnetic properties of the Co-Cr-P-Pt thin films with Cr underlayer used in longitudinal magnetic recording were characterized as a function of Pt content from 0 to 18.8 at.% Pt. The effects of platinum addition in the Co-Cr-P-Pt system on microstructural features were investigated and related to changes of magnetic properties of thin films. The increase of in-plane coercivity may be related to the segregations at the grain boundary and to the changes of other microstructural features. These changes in magnetic properties were elucidated by TEM equipped with energy dispersive x-ray spectroscopy (EDS) and Gatan Image Filter (GIF^TM). This article based on a presentation made in the symposium “The 1999 KSEA Materials Symposium in Honor of Professor Sang Joo Kim’s 70th Anniversary”, held at UCLA, Los Angeles, CA, USA, August 12–14. 1999 under the auspices of Korea—US American Scientists and Engineers Association.