合成反铁磁Ni81Fe19/Co90Fe10/Ru/Co90Fe10/Ni81Fe19的研究

采用直流磁控溅射方法制备了一系列的合成反铁磁及以其为自由层的自旋阀.研究发现,在Ni₈₁Fe₁₉与Ru层之间插入适当厚度的Co₉₀Fe₁₀层后,可有效地提高合成反铁磁两磁性层间的反铁磁耦合强度,得到具有饱和场H_s更高、饱和磁化强度M_s更低、热稳定性更好的合成反铁磁.另外,以这种合成反铁磁作自旋阀的自由层时,可有效提高自旋阀的稳定性. 关键词： 合成反铁磁 退火 自旋阀     

La0.4Ca0.6MnO3系统中Mn位Fe和Cr掺杂效应的比较性研究

利用固相反应法制备了Mn位Fe³⁺和Cr³⁺掺杂的系列锰氧化物La_0.4Ca_0.6(Mn_1-x(y)B_x(y))O₃ (B=Fe³⁺ (0≤x≤0.1); Cr³⁺ (0≤y≤0.1)) 多晶样品,研究了掺杂对样品输运性质的影响.实验结果表明两种离子具有截 关键词： 锰氧化物 反铁磁 磁电阻效应     

IrMn基反铁磁自旋阀的巨磁电阻效应

用第一性原理方法研究了在微观尺度具有三重对称磁结构的IrMn合金的反铁磁自旋阀(AFSV)的电子输运.研究表明:基于有序L1₂相IrMn合金的Co/Cu/IrMn自旋阀的巨磁电阻(GMR)效应具有三重对称性,可以利用这一特性区分反铁磁材料的GMR与传统铁磁材料的GMR.基于无序γ相IrMn合金的IrMn(0.84 nm)/Cu(0.42 nm)/IrMn(0.42 nm)/Cu(0.42 nm)(111) AFSV的电流平行平面构型的GMR约为7.7％,大约是电流垂直平面构型的GMR(3.4％)的两倍,明显大于实验中观测到的基于共线磁结构的FeMn基AFSV的GMR. 关键词： 反铁磁自旋阀 巨磁电阻效应 非共线磁结构 电流平行平面结构     

Pr2Fe14(C,B)/α-(Fe,Co)型纳米晶复合磁体的结构与磁性

研究了Pr_xFe_82-x-yTi_yCo₁₀B₄C₄ (x=9—10.5;y=0, 2)纳米晶薄带的结构与磁性. 结果表明,所有薄带皆主要由2∶14∶1, 2∶17和α-(Fe, Co)三相组成. 对于y=0的合金,其内禀矫顽力随Pr含量x的增加而增加,剩磁随Pr含量x的增加而减小. 以Ti置换部分Fe (y=2),合金的磁性能得到显著提高,表现为:添加Ti后,合金的剩磁B_r基本不降低,x=10.5时合金的B_r值甚至有较明显的提高;同时添加Ti后,合金的内禀矫顽力及退磁曲线的方形度都明显改善. 当x=10.5,y=2时,合金薄带的磁性能达到最佳值为: B_r=9.6 kGs(1 Gs=10^-4 T),_iH_c =10.2 kOe(1 Oe=79.5775 A/m)和(BH)_max＝17.4 MGOe. 随着Pr含量的提高,合金中的硬磁相2 ∶14 ∶1的含量相对增加,内禀矫顽力提高;而Ti置换Fe抑制了软磁相α-(Fe, Co)在快淬和热处理过程中的优先长大,使合金中软磁相和硬磁相的晶粒尺寸及比例趋向最佳组合,交换耦合作用明显增强. 关键词： 纳米晶永磁材料 2Fe₁₄(C')" href="#">Pr₂Fe₁₄(C B) Ti添加 交换耦合     

Co(S1-xSex)2系统中的铁磁量子相变

针对Co(S_1-xSe_x)₂系统在x=0.11附近发生的铁磁金属到顺磁金属相变,制备了一系列不同Se替代浓度的多晶样品.通过对其结构和电阻率-温度ρ(T)关系的系统观测,结果发现,样品铁磁相变温度T_C随着Se替代浓度x值的增加,以(1-x)^1/2关系单调下降,其二级铁磁相变转变为一级相变 关键词： 量子相变 自旋量子涨落 1-xSe_x)₂')" href="#">Co(S_1-xSe_x)₂     

NiS2-xSex在x=1.00附近的反铁磁量子相变

针对NiS_2-xSe_x系统在x=1.0０附近发生的反铁磁量子相变,制备了一系列NiS_2-xSe_x(x=0.96, 0.98, 1.00, 1.05, 1.10和1.20)多晶样品,对其结构、磁性质和电阻率进行了系统的观测.结果发现：样品磁化率-温度关系呈现典型的强关联电子系统特征;与铜氧化物超导体相类似,它们的电阻率-温度关系在很宽的温 关键词： 量子相变 反铁磁自旋涨落 2-xSe_x体系')" href="#">NiS_2-xSe_x体系     

La0.3Ca0.7Mn1－xVxO3体系的有序相和再入型自旋玻璃行为研究

通过对La_0.3Ca_0.7Mn_1－xV_xO₃(x=0.05,0.10,0.134,0.20)体系的M-T曲线、ρ-T曲线、ESR谱的测量,研究了Mn位掺V对La_0.3Ca_0.7MnO₃体系电荷序和自旋序的影响.结果表明,当0.05≤x≤0.134时, 体系存在电荷有序(CO)相,其自旋序随温度降低发生顺磁(PM)-电荷有序(CO)-反铁磁(AFM)变化.当x＝0.20时,CO相逐步融化,在40 K发生自旋玻璃转变,表现出再入型的自旋玻璃行为,低温下的基态存在着多种复杂的磁相互作用之间的竞争机理. 关键词： 电荷有序 自旋序 相分离 再入型自旋玻璃行为     

自旋梯状化合物Sr14(Cu1-yFey)24O41的拉曼散射谱研究

利用常规的固相合成法制备了三种Sr₁₄(Cu_1-yFe_y)₂₄O₄₁(y=0,0.03,0.05)多晶样品,其中y=0.03是单纯Fe³⁺掺杂,y=0.05是Fe³⁺和Fe²⁺混合掺杂.在100—1500cm^-1频移范围内测量了这三种样品的偏 关键词： 拉曼散射 电输运性质 自旋梯状化合物     

高磁电阻磁性隧道结的几种微制备方法研究

利用金属掩模法优化了制备磁性隧道结的实验和工艺条件，金属掩模的狭缝宽度为100 μm. 采用4 nm厚的Co₇₅Fe₂₅为铁磁电极和10或08 nm厚的铝氧化物 为势垒膜， 直接制备出了室温隧穿磁电阻（TMR）为30%—48％的磁性隧道结，其结构为Ta(5 nm)/Cu(25 nm)/Ni₇₉Fe₂₁(5 nm)/Ir₂₂Mn₇₈(10 nm)/ Co₇₅Fe₂₅ (4 nm)/Al(08 nm)-O/Co₇₅Fe₂₅(4 nm)/Ni₇₉Fe ₂₁(20 nm)/Ta(5 nm).同时，利用刻槽打孔法和去胶掀离法两种光刻技术并结合Ar离子束刻蚀及化学反应刻 蚀，制备出面积在4 μm×8 μm—20 μm×40 μm、具有室温高TMR和低电阻的高质量磁性 隧道结.300 ℃ 退火前后其室温TMR可分别达到22% 和50%.研究结果表明，采用光刻中的刻 槽打孔或去胶掀离工艺方法制备的小尺寸磁性隧道结，可用于研制磁动态随机存储器和磁读 出头及其他传感器件的磁敏单元. 关键词： 磁性隧道结 隧穿磁电阻 金属掩模法 光刻法     

La0.7Sr0.3-x□xCoO3(0≤x≤0.2)钴氧化物中锶空位诱导的自旋态转变效应

研究了锶空位对La_0.7Sr_0.3-x_xCoO₃ (0≤x≤0.2)多晶钴氧化物结构、磁性和输运性质的影响.结果表明：随着锶空位浓度x的增大,A位阳离子无序度增大,导致铁磁双交换作用减弱及反铁磁超交换作用增强,两者相互竞争,出现团簇自旋玻璃态;空位浓度超过10%后,Co—O键长迅速减小,导致晶体场劈裂能加大,大部分三价钴离子以低自旋态出现,系统基态为类超顺磁态, 关键词： 空位掺杂 钴氧化物 自旋转变     

Synchrotron radiation and polarized neutron study of the enhancement of orbital magnetic moment of Fe in the epitaxial NiFe/Ru multilayer

Epitaxial Ni₈₀Fe₂₀(5 nm)/Ru(x nm)/Ni₈₀Fe₂₀(5 nm) trilayers with thickness x = 0.5-3.0 were prepared on Al₂O₃ substrate. The structure, magnetic properties and magnetic depth profiles of the epitaxial Ni₈₀Fe₂₀(1 1 1)/Ru(0 0 0 1) multilayers were studied by X-ray diffraction, X-ray magnetic circular dichroism and polarized neutron reflectivity. A strongly enhanced orbital moment of Fe in the permalloy layer was observed at the Ru thickness of the first anti-ferromagnetic coupling, which might be due to an interference between two interfaces. At this Ru thickness, the neutron reflectivity data show a 0.8 nm layer at the interface with the magnetic moment perpendicular to the surface plane, which might be due to the enhanced spin-orbital coupling at interface.     

Morphology and magnetic properties of Fe x Co1−x /Co y Fe3−y O4 nanocomposites prepared by surfactants-assisted-hydrothermal process

Recently, we have demonstrated the successful synthesis of Fe _x Co_1−x /Co _y Fe_3−y O₄ nanocomposites with various alkaline solutions by using surfactants-assisted-hydrothermal (SAH) process. In this article, the synthesis of Fe _x Co_1−x /Co_yFe_3−y O₄ nanocomposites with their sizes varying between 20 nm and 2 μm was reported. X-ray powder diffraction (XRD) analyses showed that the surfactants, pH, precipitator, and temperature of the system play important roles in the nucleation and growth processes. The magnetic properties tested by vibrating sample magnetometer (VSM) at room temperature exhibit ferromagnetic behavior of the nanocomposites. These Fe _x Co_1−x /Co _y Fe_3−y O₄ nanocomposites may have a potential application as magnetic carriers for drug targeting because of their excellent soft-magnetic properties.     

Magnetic properties of FexCo1−x/CoyFe1−yFe2O4 composite under hydrothermal condition

The metal–ferrite composites Fe_xCo_1−x/Co_yFe_1−yFe₂O₄ are synthesized by using disproportion of Fe (II) and reduction of Co (II) by Fe⁰ under hydrothermal condition. The size of the particles of the composites decreases as the [KOH] decreasing. The composites are measured by TEM and it can be deduced that when [KOH] = 0.1, the size of the alloy body-centered cubic (BCC) in composites is 20 ± 7 nm, the size of the Cobalt ferrite (spinel) is 170 ± 50 nm. The maximal value of the saturation magnetization (Ms) of the composite is about 100.14 emu/g, which is synthesized under Co (II)/Fe (II) = 0.05, [KOH] = 1 N, T = 150 °C and t = 3 h. The value of Hc of the composite synthesized under Co (II)/Fe (II) = 0.5, t = 3 h, T = 150 °C and [KOH] = 10.2 mol/L is about 2878.19 Oe. The Fe–Co alloy is synthesized through a reduction reaction of the composites in a flowing gaseous mixture. There is a maximal value (302.9 emu/g) of the Ms for the alloys generated at 1000 °C, which is the Co_0.412Fe_0.588 alloy.     

Giant magnetoresistance of electrodeposited Cu-Co-Ni alloy films

Electrodeposition of CuCoNi alloys was performed in an acid-citrate medium. Nickel density parameter was varied in order to analyse its influence on the magnetoresistance. The structure and giant magneto-resistance (GMR) effect of CuCoNi alloys have been investigated. The maximum value for GMR ratio, at room temperature is 1% at a field of 12 kOe, and at 20 K is 2.1% at a field of 8.5 kOe for 3.1 Ni. The MR ratio of Cu_100-y-x Co_yNi_x alloys first increases and then decreases monotonically with increasing Ni content. The GMR and its dependence on magnetic field and temperature were discussed.      

R3(Fe1-xCox)29-yCry(R=Gd,Sm)化合物相稳定性研究

在制备出Gd₃(Fe_1-xCo_x)_29-yCr_{y化合物基础上，成功制备出Sm3(Fe1-xCox)29 -yCry化合物，通过x射线衍射和热磁分析对R3(Fe1-x< /sub>Co x)29-yCry 关键词： 3(Fe1-xCox)29-yCry化合物')" href="#">R3(Fe1-xCox)29-yCry化合物 相结构 单轴磁晶各向异性}     

Controlled fabrication of nano-scale double barrier magnetic tunnel junctions using focused ion beam milling method

The controlled fabrication method for nano-scale double barrier magnetic tunnel junctions (DBMTJs) with the layer structure of Ta(5)/Cu(10)/Ni₇₉Fe₂₁(5)/Ir₂₂Mn₇₈(12)/Co₆₀Fe₂₀B₂₀(4)/Al(1)–oxide/Co₆₀Fe₂₀B₂₀(6)/Al(1)–oxide/Co₆₀Fe₂₀B₂₀(4)/Ir₂₂Mn₇₈(12)/Ni₇₉Fe₂₁(5)/Ta(5) (thickness unit: nm) was used. This method involved depositing thin multi-layer stacks by sputtering system, and depositing a Pt nano-pillar using a focused ion beam which acted both as a top contact and as an etching mask. The advantages of this process over the traditional process using e-beam and optical lithography in that it involve only few processing steps, e.g. it does not involve any lift-off steps. In order to evaluate the nanofabrication techniques, the DBMTJs with the dimensions of 200 nm×400 nm, 200 nm×200 nm nano-scale were prepared and their R–H, I–V characteristics were measured.     

The effect of the sputtering process ambient on the magnetic state and phase composition of the film nanocomposites (Fe0.45Co0.45Zr0.10) x (Al2O3)1−x

The effect of oxygen-containing ambient arising at sputtering of granular nanocomposites (Fe_0.45Co_0.45Zr_0.10) _x (Al₂O₃)_1−x (30 at.%≤x≤65 at.%) on their magnetic state and phase composition has been investigated. It was shown that the presence of oxygen resulted in the formation of oxide shells preventing the ferromagnetic interaction between Co_0.45Fe_0.45Zr_0.10 nanoparticles and also the formation of metallic percolative net beyond the percolation threshold (as opposed to the films prepared in pure argon atmosphere).     

Y2(Fe1-x-y,Coy,Crx)17化合 物的结构及居里温度

通过x射线衍射及磁测量手段研究了Y₂(Fe_1-y-x,Co_y,C r_x)₁₇化合物的结 构及居里温度.研究结果表明Y₂(Fe_1-y-x,Co_y,Crx)₁₇化合物具有六 角相的Th₂Ni₁₇型结构.随着x的增加，Y₂(Fe 关键词： 2(Fe_1-y-x')" href="#">Y₂(Fe_1-y-x y')" href="#">Co_y x)_{1 7}化合物')" href="#">Cr_x)_{1 7}化合物 x射线衍射 居里温度     

填充式skutterudite化合物：BayFexCo4-xSb12的多步固相反应合成及结构

以Ba为填充原子,在x=0—3.0,y=0—0.7的组成范围内,用多步固相反应法合成了单相Ba_yFe_xCo_4-xSb₁₂化合物.用Rietveld方法对结构的精确化结果表明：合成的Ba_yFe_xCo_4-xSb₁₂化合物具有填充式skutterudite结构,Ba的热振动参数(B)比Sb,Fe/Co的大,表明在Ba_y关键词： 填充式skutterudite化合物 固相反应     

Observations of multi-phase microstructures in R2(Fe1−xCox)14B where R=Nd or Dy

Multi-phase microstructures were observed in the psuedo-quaternary phase field of the 2–14–1 magnet materials Nd₂Fe₁₄B, Nd₂Co₁₄B, Dy₂Fe₁₄B, and Dy₂Co₁₄B. At equilibrium, (Nd_1−yDy_y)₂(Fe_1−xCo_x)₁₄B had heretofore been widely assumed to be single phase where 1>x>0 and 1>y>0. In this study, three-phase microstructures were observed in (Nd_1−yDy_y)₂(Fe_1−xCo_x)₁₄B when x>0.3 and y>0.5. The Curie temperatures and peritectic decomposition temperatures for Nd₂(Fe_1−xCo_x)₁₄B are reported for several values of x in the range 1>x>0.