铁铬合金团簇点阵中与成分相关的磁性耦合（英文）

本文采用气相团簇束流沉积法制备了不同铁铬比的铁铬合金密集团簇点阵,研究了团簇点阵中复杂的多相结构和各种耦合效应.当合金中铬含量较大时,在团簇中能够观测到一种晶格失配的类四方结构,这种结构的出现导致了不同铁铬比的合金团簇中交换偏置效应的不同.随着铬的含量增加,合金团簇的交换偏置场减小,而团簇间的偶极相互作用增强.在合金团簇的铁磁-超顺磁转变温度以上,能明显观察到在类四方结构团簇中有更大的残存矫顽力与剩磁.在场冷条件下,对矫顽力和偏置场随温度变化的研究表明含有更多类四方结构的合金团簇有更好的热稳定性和更大的各向异性.     

Heusler合金Mn50–xCrxNi42Sn8的相变、磁性与交换偏置效应

研究了Mn50–xCrxNi42Sn8 (x=0, 0.4, 0.6, 0.8)多晶样品的相变、磁性和交换偏置效应.结果表明,该系列合金在室温下都具有非调制的四方马氏体结构.马氏体逆相变温度随Cr含量增加而逐渐降低. 20 k Oe磁场下的M-T曲线表明,该系列合金的磁性比较弱.两相之间的磁性差最大为△M=7.61 emu/g.磁性的变化主要与Mn-Mn间距的变化以及Ni(A位)-Mn(D位)间杂化作用的强弱有关.在低温下,马氏体相的磁性随着Cr含量增加而增强.在500 Oe的外加磁场作用下,从室温冷却到5 K,在Mn50Ni42Sn8合金中观察到高达2624 Oe的交换偏置场.随着Cr含量的增加,交换偏置场逐渐减小.当Cr含量x=0.8时,随着冷却场的增加, 5 K时的交换偏置场先迅速增加然后逐渐减小.当冷却场为500 Oe时,交换偏置场最大.这主要归因于自旋玻璃态与反铁磁性区域的界面交换耦合作用的变化.     

分子束外延生长Fe/Fe_(50)Mn_(50)双层膜的交换偏置

利用表面磁光克尔效应和铁磁共振对分子束外延生长的Fe/Fe50Mn50双层膜的交换偏置场和矫顽力进行了研究,实验结果表明,当反铁磁层厚度小于5.5!nm时,不出现交换偏置,而当大于这一厚度时,出现交换偏置;大约在7!nm时,达到极大值.随着反铁磁层厚度的继续增大,偏置场和矫顽力随Fe50Mn50膜厚的增大而下降.铁磁共振实验结果表明样品的磁性存在单向各向异性.并对上述结果进行了讨论.     

体心立方固溶体合金中的"团簇+连接原子"结构模型

为体现固溶体合金中的溶质原子产生的化学短程序,文章提出了配位数为14的团簇在体心立方(bcc)点阵中的堆垛模式,并建立了基于bcc结构的"团簇+连接原子"结构模型,用团簇成分式[团簇](连接原子)_x表述. 此模型中,与基体组元具有相对大的负混合焓的溶质原子占据团簇心部,其他原子作为连接或者替代团簇壳层基体原子. 1 ∶1结构模型[团簇](连接原子)₁由于最大程度地保证了团簇与连接原子的近邻,构成了连接原子最有效的合金化方式. 在两个实用bcc固溶体合金体系中, 1 ∶1模型指导设计了低V含量的储氢合金 V₁和低弹性模量高强度的 Nb₁合金. 关键词： 体心立方固溶体成分设计 "团簇+连接原子"结构模型 Ti-Cr-V合金 Ti-Zr-Mo-Nb合金     

H3+团簇离子与固体相互作用

报道了H3+团簇通过碳膜对产生的各种产物的测量结果.分析讨论了三原子离子团簇与固体相互作用中的电荷交换过程.证明在产物的形成中,电荷交换过程起关键作用.分析研究了H3+团簇与固体作用中的团簇效应和尾流效应. 关键词： H3+团簇 电荷交换 团簇效应 尾流效应     

分子束外延生长Fe/Fe50Mn50双层膜的交换偏置

利用表面磁光克尔效应和铁磁共振对分子束外延生长的Fe/Fe₅₀Mn₅₀双层膜的交换偏置场和矫顽力进行了研究,实验结果表明,当反铁磁层厚度小于55nm时 ,不出现交换偏置,而当大于这一厚度时,出现交换偏置;大约在7nm时,达到极大值.随着 反铁磁层厚度的继续增大,偏置场和矫顽力随Fe₅₀Mn₅₀膜厚的增大 而下降.铁磁共振实验结果表明样品的磁性存在单向各向异性.并对上述结果进行了讨论. 关键词： 分子束外延 50Mn₅₀')" href="#">Fe/Fe₅₀Mn₅₀ 双层膜 交换偏置     

Heusler合金NiCoMnSn中的磁场驱动马氏体相变、超自旋玻璃和交换偏置

合成了一系列Ni_50-xCo_xMn₃₉Sn₁₁ (8≤x≤10) 样品, 并对它们的结构和磁性进行了研究. 发现随Co含量的增加, 样品的饱和磁化强度逐渐增强, 并在Ni₄₂Co₈Mn₃₉Sn₁₁中实现了磁场诱发马氏体相变. 另外, 在Co大于8.0的成分中探测到了超自旋玻璃, 并且观察到交换偏置现象. 证实了超自旋玻璃的马氏体相和铁磁奥氏体母相共存, 这也是产生交换偏置的原因.我们猜测超自旋玻璃的形成可能是来源于Mn-Mn团簇的存在, 这和之前报道的Mn₂Ni_1.6Sn_0.4 的结果相一致^[1]. 关键词： NiCoMnSn Heusler合金 超自旋玻璃 交换偏置     

BiFeO3/Ni81Fe19磁性双层膜中的交换偏置及其热稳定性研究

研究了磁场诱导生长的BiFeO₃/Ni₁₈Fe₁₉磁性双层膜中 的交换偏置及其热稳定性. 结果表明: BiFeO₃/Ni₁₈Fe₁₉双层膜中的交换偏置场H_ex未表现出明显的磁练习效应. 在负饱和磁场等待过程中, BiFeO₃/Ni₁₈Fe₁₉双层膜磁滞回线的前支和后支曲 线都随着在负饱和磁场中等待时间t_sat的增加向正场方向偏移. 交换偏置场H_ex的大小随着等待时间t_sat的增加而减小, 矫顽力H_c基本不变. 交换偏置场H_ex的大小随测量温度T_m的升高变化不明显, 表现出良好的热稳定性; 但矫顽力H_c随T_m的升高而显著减小. 良好的热稳定性应该来源于铁电性和反铁磁性间的共同耦合作用. 关键词： 多铁性 磁性薄膜 交换偏置 热稳定性     

判定金属玻璃微观结构中的二十面体类团簇

基于Voronoi几何分形法, 分析了理想二十面体团簇和ZrCu二元金属玻璃中各种团簇的结构特点, 提出了一种判定金属玻璃原子结构中二十面体类团簇的方法. 并选取三个ZrCu 非晶成分作为研究对象, 基于Voronoi团簇, 利用该方法提取了各种构型团簇, 证实其中四种构型团簇的基本几何结构与理想二十面体相似, 并具有同样近似于理想二十面体的高致密度、高规则度和高五次对称性, 因此可称之为二十面体类团簇. 此类二十面体类团簇可作为金属玻璃的主要结构单元, 普遍存在于非晶结构中; 二十面体类团簇及其连接能包含几乎所有的原子, 从而形成非晶结构. 研究结果提供了一种新的团簇判定方法, 有助于从微观结构层面分析合金中的非晶形成机理.     

NiFe/FeMn双层膜交换偏置的形成及热稳定性研究

研究了在铁磁(NiFe)/反铁磁(FeMn)双层膜之间，交换偏置的形成过程和热稳定性，特别是NiFe/FeMn的交换偏置作用与FeMn层晶粒尺寸的关系.和以前作者不同的是，本文方法采用非磁性Ni-Fe-Cr合金作缓冲层材料，改变Cr的含量就可以获得不同晶粒尺寸的反铁磁FeMn层.实验表明，晶粒尺寸较小的FeMn产生较强的铁磁/反铁磁交换偏置场；但是，对于较大晶粒的FeMn层，出现交换偏置作用所要的临界厚度较小.这符合Mauri提出的理论模型.交换偏置场的热稳定性实验表明，具有较大晶粒尺寸的FeMn层给出较 关键词： 交换偏置 热稳定性 反铁磁 晶粒尺寸     

Magnetic cluster expansion simulation and experimental study of high temperature magnetic properties of Fe-Cr alloys

We present a combined experimental and computational study of high temperature magnetic properties of Fe-Cr alloys with chromium content up to about 20?at.%. The magnetic cluster expansion method is applied to model the magnetic properties of random Fe-Cr alloys, and in particular the Curie transition temperature, as a function of alloy composition. We find that at low (3-6?at.%) Cr content the Curie temperature increases with the increase of Cr concentration. It is maximum at approximately 6?at.% Cr and then decreases for higher Cr content. The same feature is found in thermo-magnetic measurements performed on model Fe-Cr alloys, where a 5?at.% Cr alloy has a higher Curie temperature than pure Fe. The Curie temperatures of 10 and 15?at.% Cr alloys are found to be lower than the Curie temperature of pure Fe.     

Molecular dynamics simulations of displacement cascades in Fe-10%Cr systems

Molecular dynamics simulations of the displacement cascades in Fe-10%Cr systems are used to simulate the primary knocked-on atom events of the irradiation damage at temperatures 300,600,and 750 K with primary knockedon atom energies between 1 and 15 keV.The results indicate that the vacancies produced by the cascade are all in the central region of the displacement cascade.During the cascade,all recoil Fe and Cr atoms combine with each other to form Fe-Cr or Fe-Fe interstitial dumbbells as well as interstitial clusters.The number and the size of interstitial clusters increase with the energy of the primary knocked-on atom and the temperature.A few large clusters consist of a large number of Fe interstitials with a few Cr atoms,the rest are Fe-Cr clusters with small and medium sizes.The interstitial dumbbells of Fe-Fe and Fe-Cr are in the 111 and 110 series directions,respectively.     

Molecular dynamics simulations of displacement cascades in Feben 10%Cr systems

Molecular dynamics simulations of the displacement cascades in Fe-10%Cr systems are used to simulate the primary knocked-on atom events of the irradiation damage at temperatures 300, 600, and 750 K with primary knocked-on atom energies between 1 and 15 keV. The results indicate that the vacancies produced by the cascade are all in the central region of the displacement cascade. During the cascade, all recoil Fe and Cr atoms combine with each other to form Fe-Cr or Fe-Fe interstitial dumbbells as well as interstitial clusters. The number and the size of interstitial clusters increase with the energy of the primary knocked-on atom and the temperature. A few large clusters consist of a large number of Fe interstitials with a few Cr atoms, the rest are Fe-Cr clusters with small and medium sizes. The interstitial dumbbells of Fe-Fe and Fe-Cr are in the lan111ran and lan110ran series directions, respectively.     

Temperature dependence of the giant magnetoresistance in Fe-Cr multilayers—Intralayer and interlayer exchange energies

We present field and temperature dependence data on giant magnetoresistive (GMR) ion-beam sputtered Fe-Cr multilayers of varying Cr thickness. We show that the decrease in GMR with temperature is related to the decrease in sublattice magnetization due to thermal excitation of magnons in the antiferromagnetic configuration. The intralayer and the interlayer exchange energies thus obtained vary systematically as the Cr thickness increases. The corresponding decrease in the measured saturation field further supports our interpretation leading to a better understanding of the physics of GMR.     

Fe-Cr合金辐照空洞微结构演化的相场法模拟

Fe-Cr合金作为包壳材料在高温高辐照强度等极端环境下服役,产生空位和间隙原子等辐照缺陷,辐照缺陷簇聚诱发空洞、位错环等缺陷团簇,引起辐照肿胀、晶格畸变,导致辐照硬化或软化致使材料失效.理解辐照缺陷簇聚和长大过程的组织演化,能更有效调控组织获得稳定服役性能.本文采用相场法研究Fe-Cr合金中空洞的演化,模型考虑了温度效应对点缺陷的影响以及空位和间隙的产生和复合.选择400—800 K温度区间、0—16 dpa辐照剂量范围的Fe-Cr体系为对象,研究在不同服役温度和辐照剂量下的空位扩散、复合和簇聚形成空洞的过程.在400—800 K温度区间,随着温度的升高,Fe-Cr合金空洞团簇形核率呈现出先升高后下降的趋势.考虑空位与间隙的重新组合受温度的影响可以很好地解释空洞率随温度变化时出现先升高后降低的现象.由于温度的变化将影响Fe-Cr合金中原子离位阀能,从而影响产生空位和间隙原子.同一温度下,空洞半径和空洞的体积分数随辐照剂量的增大而增大.辐照剂量的增大,级联碰撞反应加强,空位与间隙原子大量产生,高温下空位迅速的扩散聚集在Fe-Cr合金中将形成更多数量以及更大尺寸的空洞.     

Comparison of ball milling of Fe/Cr powders and Fe-Cr crystalline alloy

Using the mechanical attrition technique (MA), we have prepared a Fe-Cr alloy starting with a mixture of elemental iron and chromium powders with a nominal composition of 28 at% of Fe and 72 at% of Cr. MA was also performed on solid solutions of Fe₂₈Cr₇₂ crystalline alloy. The Mössbauer effect of the mechanically alloyed powder from Cr and Fe metals has been compared with that from crystalline alloy.     

(Ni0.81Fe0.19)1－xCrx作为种子层对NiFe/PtMn双层膜交换偏置的影响

将NiFe/PtMn双层膜生长在(Ni_0.81Fe_0.19)_1-xCr_x种子层材料上，通过改变种子层中Cr的原子含量，系统的研究了NiFe/PtMn双层膜中PtMn晶粒尺寸和织构对交换偏置的影响.对退火270℃，5h后的NiFe/PtMn双层膜磁性的研究表明,PtMn织构强弱对交换偏置场的影响不明显，而PtMn的晶粒尺寸是影响交换偏置场的主要因素，PtMn颗粒的相干长度在11.3nm左右时得到了较大的交换偏置场. 关键词： NiFe/PtMn双层膜 交换偏置场     

The Role of Intermixing in the Phase Determination of the Interlayer Exchange Coupling in Multilayers: Application to Fe-Cr Superlattices

The phase of the short-range interlayer exchange coupling oscillations in Fe n Cr m superlattices is expressed in terms of the intermixing at the Fe-Cr as well as at the Cr-Fe interfaces. The interdiffusion is modeled through stochastic algorithms, which presupposes floating of the atoms on the surface of the sample during the epitaxial growth. It automatically leads to the different chemical and magnetic structure of Fe on Cr and Cr on Fe interfaces. Self-consistent calculations of the magnetic moments are performed on the basis of the periodic Anderson model. Although short-range (2 monolayers (ML)) oscillations of exchange coupling were detected for all considered structures, its amplitude and phase strongly depend on the interface alloying. Introduction of the same intermixing at both interfaces does not change the phase as compared to the ideal superlattices with sharp interfaces. However different interdiffusion leads to the ~ -phase shift in accordance with experimental results for the Fe-Cr-Fe trilayers grown on an Fe whiskers. Distribution of magnetic moments on Fe atoms contains several distinct peaks but their position and relative area weakly depend on the alloying and interlayer exchange coupling in the superlattice. On the contrary, magnetic moments on Cr atoms are very sensitive to the intermixing and their behavior determines the strength and the phase of exchange coupling oscillations.