NiFeNb缓冲层对纳米级坡莫合金薄膜各向异性磁电阻的影响

以NiFeNb作为坡莫合金薄膜的缓冲层,用多靶磁控溅射系统制备了一系列坡莫合金薄膜样品:(Ni81Fe19)1-xNbx(t)/Ni81Fe19(20nm)/Ta(3nm),研究了Nb原子含量、缓冲层厚度、基片温度对坡莫合金薄膜各向异性磁电阻和微结构的影响。用四探针法测量薄膜样品的各向异性磁电阻值(AMR),用原子力显微镜(AFM)分析样品表面形貌,用X射线衍射仪(XRD)分析样品的相结构。结果表明,(Ni81Fe19)0.807Nb0.193缓冲层对提高坡莫合金薄膜AMR值的作用明显大于Ta缓冲层。对于Ni81Fe19厚度为20nm的坡莫合金薄膜,缓冲层中Nb含量为0.193时薄膜的AMR效应及相结构最佳;随着缓冲层厚度的增加,薄膜的AMR效应先增后减,在厚度为4nm时AMR达到最大值;随着基片温度的升高,薄膜的AMR随之增大,在温度为450℃时达到最大值,之后趋于稳定,最大AMR值达到3.76%。     

NiO插层和基片温度对超薄坡莫合金薄膜各向异性磁电阻的影响

利用多靶磁控溅射系统在康宁玻璃基片上制备了Ta(4nm)/NiO(t)/Ni81Fe19(20nm)/NiO(t)/Ta(3nm)系列坡莫合金薄膜样品,研究了NiO插层厚度、基片温度对其各向异性磁电阻和微结构的影响。利用四探针技术测量薄膜样品的各向异性磁电阻比(AMR),利用X射线衍射仪(XRD)分析样品的相结构,用原子力显微镜(AFM)分析样品的表面形貌。结果表明,由于NiO插层的"镜面反射"作用,选择适当厚度的NiO插层能够大幅度提高坡莫合金薄膜各向异性磁电阻比和磁场灵敏度。对于厚度为20nm的Ni81Fe19薄膜,当基片温度为450℃时,通过插入4nm厚的NiO插层可使AMR值达到5.01%,比无NiO插层时提高了40%。     

Y_2O_3插层对Ni_(81)Fe_(19)薄膜各向异性磁电阻的影响

以Y_2O_3作为Ni_(81)Fe_(19)薄膜的氧化插层,利用磁控溅射法制备了一系列不同插层厚度的Ni_(81)Fe_(19)薄膜样品Ta(4nm)/Y_2O_3(t)/Ni_(81)Fe_(19)(20nm)/Y2O3(t)/Ta(3nm),利用非共线四探针法测量薄膜样品的各向异性磁电阻(AMR),用振动样品磁强计测量样品的磁滞回线,利用X射线衍射仪(XRD)分析样品薄膜结构,研究了Y_2O_3插层厚度对Ni_(81)Fe_(19)薄膜各向异性磁电阻的影响。结果表明,在基片温度为450℃时,Ni_(81)Fe_(19)薄膜AMR值随插层厚度增加先增后减,在插层厚度为2.5nm时样品具有最大AMR,其值为4.61%,比无插层样品的2.69%提高了71.3%。     

基片温度对Ni_(81)Fe_(19)薄膜磁性能的影响

采用电子束蒸发法在Si(111)基片上制备厚度约为100nm的Ni81Fe19薄膜,研究了基片温度对薄膜微观结构及磁性能的影响。结果表明,随着基片温度的升高,Ni81Fe19薄膜(111)衍射峰逐渐锐化,衍射峰强度显著增强,薄膜晶粒逐渐长大;薄膜的饱和磁化强度(Ms)及面内矫顽力(Hc)随基片温度的升高均逐渐增大;随着基片温度的升高,薄膜在9GHz下的共振场(Hr)呈单调降低的趋势,而铁磁共振线宽(ΔH)则先减小后增大最后基本保持不变。当基片温度为100℃时,薄膜铁磁共振线宽具有最小值ΔH=7.44kA/m(9GHz)。     

退火处理对(FeCo)/Cu多层膜巨磁电阻及电磁性能的影响

采用直流磁控溅射法制备Ta/[(Fe89.6Co10.4)0.76 nm/Cu1.2 nm]25多层膜,X射线衍射试验结果表明,退火处理提高了薄膜的结晶度,退火温度达到550℃时,薄膜中发生Fe Co和Cu的相分离;AFM测试表明增加Ta缓冲层后可有效地降低薄膜的粗糙度;巨磁电阻(GMR)效应测量结果表明,随着退火温度的升高,样品的巨磁电阻效应呈现出先增大后减小的趋势,在350℃达到最大值-1.95%;薄膜的磁性饱和场随着退火温度的升高而变大,矫顽力亦增加,并在450℃时达到3.614×104A/m。     

磁控溅射Fe/Bi_(0.8)La_(0.2)FeO_3薄膜的交换偏置特性

利用磁控溅射法在单晶Sr Ti O3(001)基片上外延生长多铁Bi0.8La0.2Fe O3(BLFO)薄膜,研究了Fe/BLFO双层膜平面内的交换偏置和矫顽力特性受单层Fe膜厚度的影响。研究表明,在所研究的温度范围内,BLFO薄膜具有纯钙钛矿结构的单向(001)特性,基片温度为680℃时沉积的薄膜具有优异的生长取向。随Fe层厚度的增加,薄膜的偏置场平缓增大,在Fe层厚度为10 nm时具有最大值32 Oe,继续增加Fe层厚度,其交换偏置场迅速减小,然而矫顽力随Fe层的增厚持续增大。交换偏置场随Fe层厚度的变化规律可能与磁畴结构的变化有关。     

缓冲层对Fe_3O_4薄膜的结构与电磁性能影响

利用直流反应磁控溅射法制备了厚度约100 nm成分单一的Fe3O4薄膜。对薄膜样品进行XRD测试,研究了不同缓冲层对薄膜结构的影响。结果表明:Fe3O4薄膜沉积在缓冲层上时,薄膜的各衍射峰与Fe3O4的尖晶石结构的衍射峰相似,以(311)峰为主峰;对薄膜表面的AFM测试结果表明引入缓冲层使得薄膜晶粒分布均匀,表面平整度较好,且可以有效地降低薄膜表面粗糙度,在La2/3Ca1/3Mn O3上沉积时均方根粗糙度最小(RMS=1.47 nm);通过对Fe3O4薄膜磁电阻效应的测试,发现引入缓冲层的Fe3O4薄膜均呈现负磁电阻效应,电阻变化率对外加磁场的灵敏度减小;由于引入缓冲层后薄膜的晶体结构发生改变,增加了磁畴壁的移动阻力,薄膜的矫顽力和剩磁提高。     

Bi/Pt底层对Co/Ni多层膜反常霍尔效应的影响

采用直流磁控溅射法在玻璃基片上制备了一系列分别以Pt和Bi/Pt为底层的Co/Ni多层膜样品。通过研究Bi的厚度、周期层数、周期层中的Co和Ni的厚度以及退火温度对样品反常霍尔效应的影响,最终获得了霍尔效应最强、良好的霍尔曲线矩形度,同时具有良好的垂直各向异性的最佳样品Bi(1nm)/Pt(5nm)/[Co(0.3nm)Ni(0.5nm)]1/Co(0.3nm)/Pt(1nm)。实验表明,退火处理有利于增强反常霍尔效应。     

(La1-xTbx)2/3Sr1/3MnO3薄膜的巨磁电阻效应

利用脉冲激光沉积法制备了（La1-xTbx)2/3Sr1/3MnO3系列薄膜样品。在77－300K的温度范围内,对样品的微观结构、磁化强度、电阻率和巨磁电阻效应等物理性质进行了系统研究。随着Tb含量x的增大,铁磁－顺磁转变温度随之下降,在x=0. 33样品中,最大磁化场μ0H=1.2T时,观察到34％的巨磁电阻。本文对其机理进行了研究和讨论。     

Pr层厚度对纳米级Fe/Pr/Cu多层膜巨磁阻的影响

采用直流磁控溅射法制备Fe/Pr/Cu系列多层膜,在超高真空中进行热处理,测量了系列样品的结构和磁电阻。结果表明:退火温度为275℃的薄膜样品具有较好的层状结构和周期性。多层膜的层间耦合性质随Pr层的厚度增加而发生变化,巨磁电阻(GMR)效应随Pr层的厚度增加而减小。讨论了稀土Pr及Pr层的厚度对巨磁电阻效应的影响。     

Ni0.25Zn0.15Fe2.6O4种子层对NiZn铁氧体双层膜性能的影响

采用旋转喷涂法在Si(100)基片上制备Ni0.25Zn0.15Fe2.6O4(100 nm)铁氧体薄膜作为种子层,然后在种子层上采用射频磁控溅射法沉积Ni0.25Cu0.09Zn0.66Fe1.998O4(600 nm)铁氧体薄膜。研究了种子层对NiZn铁氧体双层膜微观形貌、饱和磁化强度、矫顽力、磁导率及截止频率的影响。结果表明,Ni0.25Zn0.15Fe2.6O4种子层的引入促进了NiZn铁氧体双层膜尖晶石相的晶化和晶粒生长。NiZn铁氧体双层膜的饱和磁化强度Ms为420 kA/m,矫顽力Hc为5.9kA/m,截止频率fr为1.37 GHz,磁导率μ’(300 MHz)高达202。     

富FeCo晶粒对非晶TbFeCo薄膜磁特性的影响

用磁控溅射法分别在玻璃基底和硅片上沉积Tbx(Fe85Co15)100-x(x=24.7, 40.8, 厚～20nm)薄膜和Fe51Pt49(8 nm)/ Tbx(Fe85Co15) 100-x (～70 nm)双层薄膜,研究了非晶TbFeCo薄膜中富FeCo晶粒的存在对薄膜磁特性的影响.使用磁光克尔效应(MOKE)和振动样品磁强计(VSM)测量样品的磁滞回线,观察到单层TbFeCo薄膜及FePt/TbFeCo双层薄膜中由于富FeCo晶粒的存在导致的磁化反转相分离的特征,并通过测量FePt/TbFeCo双层薄膜的小回线进一步得到了分离后的磁化反转回线,证实了本文的解释.通过改变Tb靶的溅射功率,也观察到Tb含量不同的样品中都存在磁化反转相分离的特征.     

退火对Fe_(80)Pt_(20)薄膜结构和磁性的影响

用射频磁控溅射方法在玻璃基片上制备厚度为100 nm的Fe80Pt20薄膜,研究了退火对其结构和磁性的影响。随着退火温度的升高,观察到了Fe80Pt20薄膜从fcc相到可能的hcp相的相变。并且,当退火温度高于653 K时,薄膜的饱和磁化强度和矫顽力都发生显著的变化。不同温度退火薄膜的饱和磁化强度与温度的关系曲线也表明了这一相变。     

Fe/In2O3/Fe多层膜的磁性及巨磁电阻效应

采用射频溅射方法成功制备了由过渡族元素Fe和半导体材料In2O3交替生长构成的Fe/In2O3/Fe多层膜、室温下，磁性测量结果表明样品具有超顺磁性，符合朗之万方程；磁电阻比的最大值为2.93%，遵从颗粒膜磁电阻的平方律。上述实验结果表明该多层膜样品具有类似于颗粒膜的结构。     

Giant magnetoresistance and magnetic anisotropy of Co9Fe/Cu/Co9Fe multilayer thin films on an MgO(110) substrate

Magnetoresistive effects have been investigated using Co₉Fe/Cu/Co₉Fe that were deposited on an MgO(110) substrate by ion beam sputtering with a 21-A-thick CU layer and with various thicknesses of the Co₉Fe films. The influence of a 50-A-thick Fe buffer layer has also been investigated. In addition to a cubic symmetry anisotropy (K₁), an in-plane uniaxial magnetic anisotropy (K_u) was induced, which easy axis is parallel to the (110) plane of the MgO substrate and the (001) plane with and without the 50-A-thick Fe buffer layer, respectively. The magnetoresistance (MR) ratio decreased monotonically with increasing thickness of the Co₉Fe films from 25 A to 70 A. A maximum MR ratio of 11.5 percent was obtained at room temperature. With increasing magnetic field, the MR ratio reached a plateau gradually after a steep drop at small magnetic fields without the Fe buffer layer. It reached a plateau rapidly at small magnetic fields with the Fe buffer layer. By considering both K_u and K₁, these behaviors can be accounted for by the magnetization processes involved.     

退火温度及薄膜厚度对Co-Ag颗粒膜结构及巨磁电阻效应的影响

采用磁控溅射方法制备CoxAg100-x颗粒膜,研究了其巨磁电阻(GMR)效应。结果表明,GMR效应的大小是颗粒膜厚度的函数。在0.9T外磁场下,当玻璃衬底上制备态Co33.8Ag66.2颗粒膜的膜厚为100nm时,其GMR效应值达到最大值(-18.2%),且GMR值随退火温度的上升而单调减小。     

Room Temperature Magnetoresistance at Low Magnetic Fields in La0.7 Ba0.3 MnO3

This paper examines the possibility of enhancing the room temperature magnetoresistance at low applied magnetic fields in single layer La_0.7 Ba_0.3 MnO₃ thin films. The influence of lattice mismatch strain, as well as the effect of different frequency regimes, on the magnetoresistance is explored. The effects of lattice mismatch strain are studied by measuring the magnetoresistance as a function of the La_0.7 Ba_0.3 MnO₃ film thickness, oxygen annealing, and lattice matched buffer layers. We find that the release of the lattice mismatch strain improves the magnetoresistance at room temperature and at low magnetic fields. In fact, the highest magnetoresistance at room temperature (–1.7% at 500 Oe) has been found for the 1600 Å as-grown La_0.7 Ba_0.3 MnO₃ film, whereas the largest magnetoresistance (–1.9% at 500 Oe) is found at 309 K for the 1000 Å La_0.7 Ba_0.3 MnO₃ film annealed in flowing O₂ for 1 h at 900°C. Finally, we find that the microwave magnetoresistance is the same as the dc magnetoresistance when the cavity corrections are applied. In the single layer La_0.7 Ba_0.3 MnO₃ system, the low field magnetoresistance at room temperature is far from being technologically viable.     

制备条件对Fe-Ta-N薄膜的结构和软磁性能的影响

应用射频磁控溅射法制备了Fe-Ta-N薄膜,系统地研究了制备工艺地Fe-Ta-N薄膜结构和软磁性能的影响,首先,制备了不同钽含量的薄膜,发现（Fe89.5Ta10.5）-N薄膜具有很好的软磁性能,氮分压P（N2）=5%时,矫顽力获得最小值,Hc=14A/m。此时,样品呈现纳米晶结构,晶粒尺寸D≤10∧-8m,并且,钽掺杂能抑制铁氮化合物的生成,使薄膜在高氮分压范围内具有高的饱和磁化强度,Ms=1242kA/m。其次,考察了热处理对（F89.5Ta10.5）-N薄膜结构和磁性能的影响,P(N2）=5%时,沉积态薄膜为非晶结构,矫顽力很大;在热处理过程中,薄膜逐渐晶化,400℃热处理后,晶化度达到40%,形成纳米晶结构,矫顽力迅速减小,最后,比较了不同溅射功率和总气压对（Fe89.5Ta10.5）-N薄膜结构和磁性能的影响,发现薄膜可在较大的溅射功率和总气压范围内保持优异的软磁性能,是非常适于工业生产的薄膜磁头材料。     

Magnetoresistance effect in PP + Fe based nanocomposite system

The article investigates the acqusition, structure, magnetic properties and magnetoresistance effect of nanocomposites on the basis of polypropylene matrix and iron nanoparticles, structure, magnetic properties and magnetoresistance. AFM results illustrate that the increase in the volume content of Fe nanoparticles in the polymer matrix causes changes on its supramolecular structure. As a result of the MFM studies, it has been defined that, nanoparticles dispersed in the polymer matrix form domains in the local areas and the sizes of domains vary from 150 to 400?nm. The study of magnetic properties of PP?+?Fe based nanocomposites showed that intrinsic magnetization increases with increasing magnetic field intensity and saturation occurs at certain value of intensity. If the field is reduced, remanent magnetization and hysterezis loop is observed. The dependence of PP?+?Fe based nanocomposites on the magnetic field was investigated and magnetoresistive effect was observed and it was found to be related with the presence of tunneling magnetoresistance effect in these nanocomposites.