超细Co/Cu纳米多层膜磁性研究

利用磁控溅射方法制备了纳米Co/Cu多层膜。利用扫描探针显微镜(SPM)观测了其表面形貌和磁畴结构,并通过振动样品磁强计(VSM)测量了磁性。结果表明,薄膜的微结构和磁性随非磁性层厚度的变化有着非常显著的变化。超细Co颗粒构造的多层膜样品,颗粒尺寸逐渐增大,磁畴尺寸先减小后增大,最后发生明显的聚集。磁性金属和非磁性金属的比例对多层膜之间的交换耦合相互作用有显著影响。平行膜面方向上的饱和场明显小于垂直膜面方向。当体积比约为1∶80时,平行膜面方向饱和场为95.9 kA/m,垂直方向饱和场为328.1 kA/m。此时两个方向上的饱和场、剩磁、矫顽力和磁滞损耗均为最小值。     

磁场退火对FePt/Ag薄膜磁性能的影响

采用磁控溅射法室温沉积获得FePt/Ag薄膜,然后在500℃下,于真空磁退火炉中对薄膜进行退火处理。利用XRD和振动样品磁强计(VSM),研究了磁场退火对薄膜结构和磁性能的影响。结果表明,500℃零磁场退火获得了矫顽力为0.763 4 MA.m–1、平均晶粒尺寸21 nm的L10-FePt薄膜。磁场提供了FePt成核生长的驱动力,0.8 MA.m–1磁场退火后FePt的平均晶粒尺寸为26 nm,矫顽力增大至0.804 3 MA.m–1。非磁性Ag的掺杂可有效抑制磁性FePt晶粒的团聚生长。     

磁控溅射法制备Ag/FePt/C/FePt薄膜的结构和磁性能

采用磁控溅射法,在自然氧化的Si(001)基片上沉积了Ag/FePt/C/FePt纳米薄膜,并分别在400,450,500,600℃下对薄膜样品进行了1h的退火热处理。利用X射线衍射仪和振动样品磁强计,对薄膜样品的结构和磁性进行了分析。结果表明,当热处理温度为450℃时,Ag/FePt/C/FePt薄膜中已形成了具有有序面心四方结构的L10-FePt。随着热处理温度的升高,薄膜样品的有序化程度提高,矫顽力Hc增强,晶粒尺寸变大。当热处理温度为600℃时,薄膜样品的平行膜面Hc为905.8kA·m-1,晶粒尺寸为23nm。     

磁控溅射制备Co1-xPtx:C复合纳米颗粒薄膜的研究

采用组合靶，利用磁控共溅射技术制备了Co1-xPtx：C复合纳米颗粒薄膜，并从实验和理论上对不同Pt浓度CoPt：C薄膜的组分、微结构、磁性能、组分和微结构与磁性能之间的关系以及薄膜的应用进行了初步研究。发现CoPt粒子取向和磁性能与CoPt：C薄膜中的Pt浓度有密切关系，在较高Pt浓度的CoPt：C薄膜中观察到垂直各向异性现象。通过改变Pt浓度，可以获得粒子粒径小于10nm、矫顽力可控、垂直磁晶各向异性较高的薄膜。晶格结构和晶粒之间的作用力可认为是影响CoPt：C薄膜磁性能的主要因素。     

SiO2含量对FeCo/SiO2复合薄膜结构和磁性能的影响

采用溶胶-凝胶旋涂法并结合氢气还原工艺,在Si(001)基片上制备了FeCo/SiO2复合薄膜,利用X射线衍射、原子力显微镜和振动样品磁强计研究了 SiO2含量对薄膜样品的结构、形貌和磁性能的影响。结果表明,随着SiO2含量的增加,FeCo/SiO2薄膜中FeCo的晶粒尺寸减小,样品的矫顽力呈现先略有降低然后增加的趋势。当w(SiO2)低于43%时,FeCo具有较明显的(200)晶面择优取向。当w(SiO2)为23%时,FeCo的(200)晶面择优取向度最高,样品的矫顽力最小,复合薄膜具有较好的软磁性能和较大的垂直磁晶各向异性。     

应力对厚30 nm的FeCoSiB薄膜影响的微磁模拟

从微磁学理论出发,建立了单轴应力作用下的等效模型;利用美国国家标准技术协会(NIST)开发的微磁学软件OOMMF,从理论上研究应力对厚30nm的FeCoSiB非晶磁弹性薄膜图形化单元磁畴、剩磁、矫顽力等磁性特性的影响。结果表明,FeCoSiB非晶磁弹性薄膜的磁矩分布随应力的变化明显不同;当应力于外磁场方向平行时,薄膜单元的矫顽力和剩磁随张应力的增加而线性增加,随着压应力的增加而线性减小。     

利用MFM研究薄膜厚度对Co60Fe20B20薄膜磁畴结构的影响

本文利用磁力显微镜(MFM)主要研究了由磁控溅射法制备的Co60Fe20B20软磁薄膜的厚度变化(2.5nm～400nm)对薄膜磁畴结构的影响.在室温下观察到垂直各向异性随薄膜厚度的增大而增大.从薄膜的表面形貌像观察到在溅射过程中薄膜温度随薄膜厚度增大而升高.当薄膜厚度小于20nm时,磁畴尺寸随薄膜厚度的增大而增大;当薄膜厚度大于20nm时,磁畴尺寸随薄膜厚度的增大而减小;厚度在20nm附近时,畴壁尺寸达到一个最小值.     

空心Fe3O4磁性纳米颗粒的制备及其磁性表征

本文采用溶剂热法以尿素作为沉淀剂和模板剂成功制备了一系列内外径可控的空心Fe3O4磁性纳米颗粒。利用透射电子显微镜(TEM)、X射线衍射仪(XRD)、振动样品磁强计(VSM)对所制备的Fe3O4磁性纳米颗粒的形貌、结构及其宏观磁性进行了详细的表征。TEM结果显示,该方法制备的Fe3O4磁性纳米颗粒均呈现内部空心结构,外径约为615 nm,内径约为310 nm,且尺寸均匀,分散性良好;样品的饱和磁化强度Ms=90.4 emu/g,矫顽力He=62.5 Oe呈现铁磁性。同时发现,Fe3O4粒径随尿素加入量的增大而减小。本文报道的空心结构的Fe3O4磁性纳米颗粒有望在纳米医学及纳米生物学上具有广泛的应用前景。     

热处理对NiP/CoNiP薄膜织构和磁性能的影响

用化学镀的方法制取了NiP/CoNiP薄膜并将样品进行真空热处理。用XRD、VSM、EDS等测试手段分析了热处理影响薄膜结构和磁性能变化的原因。结果发现,热处理使薄膜的结构发生了由α-Co向β-Co的同素异构转变;经热处理后晶粒尺寸长大到30 nm左右;经350℃热处理后薄膜的矫顽力升高到5.57×104 A/m;经400℃热处理后矩形比达到0.28。     

还原温度对纳米FeCo/Al2O3复合薄膜结构和磁性的影响

采用溶胶-凝胶旋涂法和H2还原工艺制备了纳米FeCo/Al2O3复合薄膜.利用X射线衍射仪、扫描电子显微镜、原子力显微镜及振动样品磁强计研究了还原温度对薄膜结构、表面形貌和磁性的影响.结果表明,随着还原温度的升高,薄膜中FeCo的晶粒尺寸和晶格常数变大,薄膜的饱和磁化强度(Ms)也同时增大,其矫顽力(Hc)则先增大,后...     

Carbon‐Decorated FePt Nanoparticles

FePt magnetic nanoparticles are an important candidate material for many future magnetic applications. FePt exists as two main phases, that is, a disordered face‐centered cubic (fcc) structure, which is generally prepared by chemical methods at low temperatures, and the high‐temperature chemically ordered face‐centered tetragonal (fct) structure. The fcc FePt, with low coercivity but associated with superparamagnetic properties, may find applications as a magnetic fluid or as a nanoscale carrier for chemical or biochemical species in biomedical areas, while fct FePt is proposed for use in ultrahigh‐density magnetic recording applications. However, for both of these applications an enhancement of the intrinsically weak magnetic properties, the avoidance of magnetic interferences from neighbor particles, and the improved stability of the small magnetic body remain key practical issues. We report a simple synthetic method for producing FePt nanoparticles that involves hydrothermal treatment of Fe and Pt precursors in glucose followed by calcination at 900 °C. This new method produces thermally stable spheroidal graphite nanoparticles (large and fullerene‐like) that encapsulate or decorate FePt particles of ca. 5 nm with no severe macroscopic particle coalescence. Also, a low coercivity of the material is recorded; indicative of small magnetic interference from neighboring carbon‐coated particles. Thus, this simple synthetic method involves the use of a more environmentally acceptable glucose/aqueous phase to offer a protective coating for FePt nanoparticles. It is also believed that such a synthetic protocol can be readily extended to the preparation of other graphite‐coated magnetic iron alloys of controlled size, stoichiometry, and physical properties.     

Fe/TiO_2纳米复合物的制备、表征及其性能

采用溶胶-凝胶结合氢气还原方法,制备了Fe与TiO2两相共存的纳米复合物。透射电子显微镜(TEM)图片显示,纳米复合物的颗粒大小为100~300nm,且具有明显的核/壳结构。X射线衍射结果表明,纳米复合物中存在a-Fe与金红石型TiO2结构,未发现其他杂相。振动样品磁强计(VSM)的测量结果表明,样品具有较高的比饱和磁化强度。研究表明,通过控制前驱物的用量,能有效改变样品的磁性。热重分析(TGA)结果表明,样品具备很好的抗氧化性。复合介电谱和磁谱表明,在测量的微波频率范围内,样品的介电损耗大于磁损耗。     

FePt纳米粒子有序膜结构的SPM研究

采用化学合成方法制备了单分散的FePt磁性纳米粒子，通过对纳米粒子的操纵与排布制得了磁性纳米粒子单层膜和多层膜，并利用扫描探针显微技术(SPM)和X射线粉末衍射(XRD)考察了磁性纳米粒子膜中FePt纳米粒子的形貌、粒度分布和表面聚集状态。研究结果表明在磁性纳米粒子单层膜中，磁性纳米粒子分布均匀、排列紧密，且多层膜在膜累加方向是具有周期结构的有序组合体。     

利用有机覆盖层提高OLED出光效率

将Alq作为覆盖层真空蒸镀到玻璃基板后制作底发射有机电致发光器件(OLED),所制备的器件结构为:Glass/Alq(xnm)/Al(15nm)/MoO3(30nm)/NPB(60nm)/Alq(65nm)/LiF(1nm)/Al(150nm)。通过研究器件光辐射特性曲线,可以看出覆盖层厚度的变化引起光的干涉效应的变化是导致电致发光变化的原因,广角干涉和多光束干涉之间的相互作用可以通过覆盖层的厚度来调节,并且半透明的Al膜做阳极,将覆盖层蒸镀到阳极之外玻璃基板上,半透明的铝膜和覆盖层与阴极组成微腔器件,通过改变覆盖层的厚度调节微腔的腔长,使OLED电致发光光谱的中心波长发生红移。     

Integrated solenoid inductors with patterned, sputter-deposited Cr/Fe/sub 10/Co/sub 90//Cr ferromagnetic cores

Ferromagnetic (FM) films suitable for implementation in between interconnect layers of a standard CMOS fabrication process are demonstrated to yield considerable size reduction of monolithic radio frequency (RF) inductors, leading to lower cost. The deposition of a FM Cr(5 nm)/Fe/sub 10/Co/sub 90/(500 nm)/Cr(15 nm) stack is performed by magnetron sputtering at room temperature under a dc magnetic field of /spl sim/ 10 mT along the magnetic easy-axis. A lift-off technique, using a four-layer shadow mask, is used for pattern transfer to the magnetic stack to circumvent apparent difficulties in the patterning of FM films. A series of solenoid-type inductors with FM cores are demonstrated and compared to control devices with air cores. A more than eight-fold enhancement of the inductance and a seven-fold improvement of the quality factor are achieved.     

Control of the formation of ultrathin CoSi<Subscript>2</Subscript> layers during the rapid thermal annealing of Ti/Co/Ti/Si(100) structures

The initial Ti(8 nm)/Co(10 nm)/Ti(5 nm) structures formed on the Si(100) substrate by magnetron sputtering were subjected to two-stage rapid thermal annealing (RTA) in the nitrogen ambient. The samples of the structures were controlled using the time-of-flight SIMS, the Auger spectroscopy, scanning electron microscopy, X-ray dispersion microprobe analysis, and measurements of the layer resistance at each stage of annealing. At the RTA-1 stage (550°C, 45 s), a sacrificial layer formed on the surface. This layer consisted of the titanium (oxy)nitride coating, into which the residual impurities (O, C, and N) were forced out, and the transient Co-Si-Ti(TiO,TiN) layer with a high cobalt content and a low (trace) titanium content. After the selective removal of this sacrificial layer, the surface composition corresponded to monosilicide CoSi, which transformed into the highly conductive CoSi₂ phase at the RTA-2 stage (830°C, 25 s).     

双量子阱OLED正负磁电阻的调控

通过改变发光层的厚度,制备了一种双量子阱结构的有机电致发光器件(OLEDs),其结构为ITO/2T-NATA(20nm)/NPBX(50nm)/[Alq3:2%C545(dnm)/Alq3(3nm)]2/Alq3(17nm)/LiF(0.9nm)/Al。在常温下研究了器件的发光层在不同厚度(d=10,15,20和25nm)时的磁电阻(MR,magnetoresistance)特性。实验结果表明,在10V驱动电压的作用下,在相同磁场强度下,器件的厚度越大,电阻率也越大;在驱动电压为10V时,随着磁场强度的增加,10nm厚器件的MR随着磁场的增加而增大,表现正MR特性;而15、20和25nm厚3种器件的MR随着磁场强度的增强先减小后增加并趋于饱和状态,发光层越厚,MR减小的幅度越大,且都表现出负MR特性;获得最大的MR为-10.32%。