沉积厚度对L10-FePd颗粒膜结构和磁性能的影响

采用直流磁控溅射法在石英玻璃基片上制备不同厚度的FePd纳米颗粒膜,利用X射线衍射仪、X射线能谱仪、扫描电子显微镜、原子力显微镜和振动样品磁强计表征薄膜的结构和磁性能。结果表明,经过550℃热处理3h后,薄膜的X射线衍射谱中出现(002)超晶格衍射峰,表明薄膜中出现了四方有序结构。随着薄膜厚度的减小其有序化程度增加,在膜厚为47nm时,样品矫顽力达到3.5kOe,剩磁比达到0.94,最大磁能积((BH)_(max))达到17.6 MGOe。FePd薄膜的相转变温度降低,磁性能较好。     

Effect of Ag underlayer on microstructures and perpendicular magnetic properties of CoPt nanocomposite thin films

CoPt/Ag films were prepared by magnetron sputtering on glass substrates and subsequent annealing. The dependence of degree of ordering and magnetic properties on Ag film thickness and annealing conditions were investigated. It was found that the Ag underlayer played a dominant role in inducing the (001) texture of the CoPt film after annealing. CoPt films with a thickness about 20 nm and Ag underlayers with a thickness about 70 nm are easy to obtain a large degree of ordering and a perpendicular magnetic anisotropy after annealing at 700 degrees C for 30 min. CoPt/Ag films with out-of-plane coercivity (Hc (perpendicular)) in the range of 13.5-14.0 kOe and a out-of-plane squareness (S(perpendicular)) of 0.97 were obtained after annealing at 700 degrees C for 30 min. Ag underlayer is beneficial to enhance the Hc(perpendicular)and S(perpendicular) of CoPt film significantly. The degree of ordering and perpendicular magnetic properties of the CoPt films which deposited on Ag underlayer are larger than those of the single layer CoPt films.     

High resolution magneto-optical studies of the intermediate state in thin film superconductors

The structure of the intermediate state in superconducting lead films has been investigated as a function of magnetic field and film thickness. The detection system utilized the high specific Faraday rotation in thin films of a mixture of EuS and EuF₂ in combination with a polarizing microscope, yielding a resolution of about 1 μm. The thickness of the Pb films ranged between 0.7 and 9 μm, thus including the critical film thickness at which the transition from the intermediate state to the vortex state occurs. At low fields a liquid-like mixed state of multi-quanta flux tubes was observed which appeared to be stable up to increasing magnetic fields with decreasing film thickness. The diameter of these flux tubes varied approximately with the square root of the film thickness. At intermediate fields the intermediate state pattern was found to persist down to a film thickness of 0.7 μm, the smallest thickness investigated. The periodicity length of the intermediate state structure was in reasonable agreement with the non-branching model of Landau. Just below H_c, small superconducting domains were observed in increasing field, whereas long threads of superconducting material were formed abruptly in decreasing field. These superconducting threads were absent in the specimentsthinner than 1–2μ, being replaced by a liquid-like mixed state of superconducting tubes. After the passage of a sufficiently high electrical current through the specimen, the flux structure was found to be rearranged into long domains oriented predominantly perpendicular to the current, leading to current hysteresis effects. Finally, some dynamic observations were made during current induced flux flow.     

SmCo薄膜磁控溅射沉积速率的影响因素

SmCo薄膜的厚度是影响其磁性能的重要因素,而沉积速率是控制薄膜厚度的关键。采用直流磁控溅射工艺制备SmCo薄膜,设计正交实验并通过数理统计方法研究了溅射工艺参数中溅射功率、靶基距及氩气压强对SmCo薄膜沉积速率的影响,并同时考察了不同厚度SmCo薄膜的磁性能变化规律。研究结果表明:溅射功率与靶基距都对薄膜的沉积速率有较大的影响,其中在溅射功率为40~120W范围内时,随着溅射功率的增大SmCo薄膜的沉积速率逐渐提高;在靶基距为50~70mm的范围内,SmCo薄膜的沉积速率随靶基距的增大而逐渐降低;而在氩气压强处于0.7~1.5Pa范围内时,SmCo薄膜的沉积速率几乎不随氩气压强的改变而变化。在溅射功率为80W、靶基距为60mm及氩气压强为1.1Pa的工艺条件下,SmCo薄膜的沉积速率具有很好的稳定性。随膜厚从0.59μm增加到0.90μm,SmCo薄膜的矫顽力由23.4kA/m降低到8.2kA/m。     

Thickness dependent electronic structure of ultra-thin tetrahedral amorphous carbon (ta-C) films

Microstructural properties of ultrathin (1-10 nm) tetrahedral amorphous carbon (ta-C) films are investigated by Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, X-ray Photoelectron Spectroscopy, Raman spectroscopy and Atomic Force Microscopy (AFM). The CK-edge NEXAFS spectra of 1 nm ta-C films provided evidence of surface defects (C―H bonds) which rapidly diminish with increasing film thickness. A critical thickness for stabilization of largely sp³ matrix structure distorted by sp² sites is observed via the change of π*C═C peak behavior. Meanwhile, an increase in the film thickness promotes an enhancement in sp³ content, the film roughness remains nearly constant as probed by spectroscopic techniques and AFM, respectively. The effect of thickness on local bonding states of ultrathin ta-C films proves to be the limiting factor for their potential use in magnetic and optical storage devices.     

Effect of thickness on the properties of FeAlN films

The magnetic properties, microstructure, and morphology of thin nanocrystalline FeAlN films synthesized by RF magnetron sputtering were studied as dependent on the film thickness. The best soft magnetic properties were observed for the films with thicknesses above 800 nm. These films consist predominantly of nanocrystalline α-Fe particles with an average size of ∼15 nm and are characterized by crystal lattice expansion in the (110) plane approaching a critical level of 0.28%. FeAlN films with a thickness of 1000 nm are characterized by μ₁ ∼ 2000.     

Random Magnetic Anisotropy Studies in SmCo<Subscript>5</Subscript> Thin Films

SmCo₅ thin films with different thicknesses were prepared by electron beam evaporation on Kapton substrates. The out-of-plane hysteresis loops for different thicknesses reveal a maximum coercive field when the thickness is 15 nm. Using random magnetic anisotropy model, the thickness dependence of magnetic properties was studied in SmCo₅ nanocrystalline films and several fundamental magnetic parameters were extracted. We have determined the local magnetic anisotropy constant K ₁ which is found to increase with increasing film thickness except for t =?7 nm which is thought to arise from the structural imperfection of the SmCo₅ films.     

溅射非晶态薄膜磁性的控制

微电子技术的迅速发展要求电子元件薄膜化,从而促进了磁性薄膜的发展.为了达到控制溅射非晶态薄膜磁性的目的,从溅射非晶态薄膜的组成成分、溅射工艺参数、基体材料及温度、膜层厚度和镀后热处理工艺等几方面论述了影响非晶态溅射薄膜磁性的因素,结果表明,薄膜组成、膜厚、基材、溅射工艺及镀后热处理对溅射非晶态薄膜的磁性有较大的影响,应根据不同磁性要求加以控制.     

Asymmetry of the Pinning Force in Thin Nb Films in Parallel Magnetic Field

The pinning force, F _p, is studied in Nb films of different thickness in parallel magnetic field H. The asymmetry in the magnetic field dependence of F _p has been observed for two opposite directions of the transport current. The effect is less pronounced for thin and thick films where, respectively, single vortex pinning and pinning of the internal vortices, is relevant. At intermediate thickness, where the pinning mechanism is mostly caused by surface effects, an asymmetry in the F _p(H) dependence is clearly visible. The different surface barriers that vortices should overcome to enter the sample from opposite sides of the film explain the effect, as confirmed by numerical calculations. These have been obtained by solving the Ginzburg?CLandau equations with asymmetric boundary conditions which take into account the different superconducting properties of the film?Csubstrate and film?Cvacuum interface. Such difference can also explain the reduction of the critical current usually observed in thin films as a function of their thickness.     

铁电相BiFeO3对多铁复合薄膜CoFe2O4-BiFeO3铁磁性能的影响

为了研究铁电相BiFeO₃对复合薄膜磁性能的影响,在LaNiO₃ (LNO)缓冲层的Si (100)衬底上旋涂制备了含有0、6、9、10层等不同厚度BiFeO₃的层状CoFe₂O₄-BiFeO₃ (CFO-BFO) 多铁复合薄膜。采用XRD、SEM以及TEM对其结构和形貌进行了表征,采用振动样品磁强计测量磁性,研究了不同厚度BFO对复合薄膜磁性的影响。结果表明: CFO和BFO在异质结构薄膜中共存。缓冲层LNO和铁磁相CFO薄膜具有精细微观结构及明显界面。铁电相BFO的厚度对CFO-BFO复合薄膜的磁性能产生了很大影响。在含有不同层数铁电相BFO的复合薄膜中,含有9层BFO复合薄膜的饱和磁化强度最大,达到了230 emu·cm^-3,相比无铁电相BFO的薄膜,饱和磁化强度提高了18.6%。初步讨论认为: 随着铁电相BFO厚度的增加,CFO与BFO之间的应力传导引起了复合薄膜饱和磁化强度的提高。     

Magnetic properties of mismatched coupled films

Magnetically coupled thin films have proven useful in the development of high density NDRO magnetic thin film memory devices. This communication reports the variation in magnetic properties of both films comprising the film pair as a function of the interlayer thickness.     

溅射法制备Mn-Zn铁氧体薄膜的磁性与微结构

以交替真空溅射的方法使用成分分别为MnFe2O4与ZnFe2O4的双靶制备了成分变化的系列Mn1-xZnxFe2O4铁氧体薄膜,衬底为Si(100)。薄膜的成分通过控制不同靶的溅射时间来进行调整。沉积态的薄膜呈非晶结构,在真空炉中以适当的温度对薄膜进行退火之后能够得到多晶Mn-Zn铁氧体薄膜。组成成分为Mn0.5Zn0.5Fe2O4的薄膜呈现了相对最高的饱和磁化强度。同时还研究了制备条件对薄膜结构与磁性的影响,如溅射氧分压,退火真空度,退火温度及薄膜厚度等等。制备的薄膜相对于块状材料具有较高的矫顽力,进而讨论了应力对薄膜矫顽力的影响。     

The magnetic anisotropy of thin epitaxial CrO<Subscript>2</Subscript> films studied by ferromagnetic resonance

The magnetic anisotropy of thin epitaxial films of chromium dioxide (CrO₂) has been studied as a function of the film thickness by the ferromagnetic resonance (FMR) technique. CrO₂ films with various thicknesses in the range from 27 to 535 nm have been grown on (100)-oriented TiO₂ substrates by chemical vapor deposition using CrO₃ as a solid precursor. In a series of CrO₂ films grown on the substrates cleaned by etching in a hydrofluoric acid solution, the FMR signal exhibits anisotropy and is strongly dependent on the film thickness. The magnetic properties of CrO₂ films are determined by a competition between the magnetocrystalline and magnetoelastic anisotropy energies, the latter being related to elastic tensile stresses caused by the lattice mismatch between the film and the substrate. In the films of minimum thickness (27 nm), this strain-induced anisotropy is predominant and the easy magnetization axis switches from the [ 001] crystallographic direction (characteristic of the bulk magnet) to the [ 010] direction.     

Magnetic properties of sputtered soft magnetic Fe–Ni films with an uniaxial anisotropy

The microstructure and magnetic properties of polycrystalline Fe_100−xNi_x films have been studied by X-ray diffraction (XRD) and magnetic moment measurements. In the XRD pattern of Fe–Ni films, the values of area ratio, A(1 1 1)/A(2 0 0) for the XRD peaks, in the thickness dependence decrease rapidly with increasing film thickness in the films with a bias field applied parallel to the plane in order to introduce uniaxial anisotropy, but the values for the films without the field are nearly constant. The coercivity vs. thickness analyzed by using Néel's formula show that the values for the films with the bias field follow Néel's formula within the thickness range of 40–100 nm, except the range of 10–40 nm. This result indicates that there is a change in domain wall type at the thickness of 40 nm. From the results of thickness and temperature dependence of magnetization analyzed by using some theoretical models, the values of interaction strength between magnetic ions were determined. The electrical resistivity of films is found to be consistent with the Mayadas–Shatzkes model.     

Structure and magnetic properties of Fe films with pyramid-like nanostructures deposited by oblique target direct current magnetron sputtering

Fe thin films were deposited by oblique target direct current magnetron sputtering on Si (100) and (111) substrates. The structure, surface morphology and magnetic properties of the thin films were characterized using X-ray diffraction, field emission scanning electron microscopy, and superconducting quantum interference device magnetometer, respectively. The results reveal that the structure of the as-deposited Fe thin films is body-centered cubic with the preferential [110] crystalline orientation. A pyramid-like nanostructure with sharp tip was formed on the surfaces of Fe thin films under appropriate sputtering power. Formation of the pyramid-like nanostructure is mainly owed to the enhancement of atomic mobility and the bombardment effect with increasing of sputtering power. Meanwhile, the crystalline orientation of Si substrate and the intrinsic stress in the films are expected to have little contribution to the formation of the pyramid-like nanostructure. The magnetic anisotropy was found in the as-deposited Fe thin films, and varies with the thickness of the Fe thin films. As the film thickness increases from 604 to 1,786 nm, the magnetic anisotropy field and the uniaxial anisotropy constant increase from 3.8 to 5.6 kOe, and from 0.4 × 10⁶ to 1.1 × 10⁶ erg/cm³, respectively, which indicates that besides magnetocrystalline anisotropy, stress induced anisotropy and shape anisotropy also exist in the as-deposited Fe thin films.     

Surface morphology and optical properties of magnetron - sputtered ultrathin Al films

Ultrathin Al films with different thicknesses were deposited on glass substrates by DC magnetron sputtering. The effects of film thickness on morphology and optical properties of the films were investigated in detail. When film thickness increases from 7.0 to 84.0 nm, the average grain size and surface roughness enlarges from 27.6 to 94.2 nm and from 0.25 to 1.87 nm, respectively. Below critical thickness of 28.0 nm, which is the thickness that Al films form continuous film, the optical properties vary significantly with thickness increasing and then tend to be stable. In the absorptance spectra, all films exhibit distinct broad peaks which can be attributed to the absorption due to the interband transition. The possible reasons for the shift in the peak position are due to the quantum size effects and internal stress in the ultrathin Al films.     

Preparation and magnetic properties of electrodeposited [Co/Zn] multilayer films

In this report we describe some experimental results concerning the preparation by electrodeposition and characterization of Co/Zn multilayer films, a system of special significance because Co and Zn are immiscible in a large range of compositions, permitting an easier adaptation of the sharp interfaces and the magnetic interactions between layers, with a view to obtain technological applications in nano-electronics. We established the working parameters for electrodeposition of multilayer films based on Co and Zn nanoscale layers, using a dual-bath potentiostatic electrodeposition method. The effect of the first electrodeposited layer growth process on the structure and magnetic properties of the multilayer were studied by using two series of multilayers of varying periods, starting with Co or Zn layers, respectively (with the same total thickness of Co layers, namely 50 layers of 5 nm thick, but various Zn layer thickness). These properties were also studied as a function of the Zn layer thicknesses (varying between 0.1 nm and 5.9 nm), for the two series of films. The magnetoresistance (in the current in plane configuration with dc magnetic field applied in the film plane), varied with Zn layer thickness, exhibiting a giant magnetoresistance contribution of about 30% in the case of [Co (5 nm)/Zn (2.7 nm)]₅₀ films.     

Magnetic and optical properties of amorphous NdFeCo thin films by pulsed laser deposition technique

Rare earth and transition metal doped (NdFeCo) thin films were fabricated on Si (100) substrate by pulsed laser deposition technique keeping the substrate at constant temperature of 300 °C. A KrF Excimer laser (248 nm, 20 ns) was used as an energy source for the deposition. Thin films were deposited without and under the influence of transverse magnetic field applied across the plume. The applied magnetic field was varied from 3 to 6 kOe. The deposited films were characterized by XRD, FESEM, VSM and SE (Spectroscopic Ellipsometry). The deposited films were amorphous in nature. All the films regardless of the applied magnetic field exhibit perpendicular magnetic anisotropy. The thickness of the thin films was found to increase monotonically from 166 to 266 nm with the increase in the applied external magnetic field. The saturation magnetization has a maximum value of 1682 emu/cc for the film deposited under 4.5 kOe magnetic field. The value of optical band gap energy for the same film is found to have a maximum value of 3.1 eV. The values of both the saturation magnetization and the band gap energy were decreased with the increase in the applied magnetic field.     

The preparation and properties of electrodeposited permalloy films on substrates of evaporated permalloy

The technology of production and some of the properties of isotropic magnetic Ni 80%-Fe 20% films are described. These films were obtained by permalloy electrodeposition onto glass substrates previously coated with vacuum-deposited thin films of Ni-Fe alloy. The change in the magnetoresistance of the films as a function of thickness has been investigated and is discussed, taking into account the influence of the film composition. The results are compared with those previously reported for evaporated films. The dependence of coercive force on film thickness is given. An increase in the crystallite size of the electro-deposited films with respect to the vacuum-deposited substrate has been found.     

Dynamic crosstie nucleation thresholds for crosstie memory

Pulsed magnetic fields (widths of 1 to 550 ns) with amplitudes above a threshold value will generate crossties [1] in Permalloy films (∼300 to 500 Å). Pulse width and film thickness affect the threshold values, which decrease with increasing pulse width and increasing film thickness. Fig. 2 shows typical behavior.