应力生长FeCoSiB非晶薄膜的磁各向异性研究

采用应力生长方法，制备出受压应力和张应力作用的FeCoSiB非晶磁弹性薄膜，研究了薄膜中的应变大小对FeCoSiB薄膜的磁滞回线、剩磁、应力诱导各向异性场等磁特性的影响．结果表明，无应变薄膜在薄膜面内呈现各向同性，而有应变的薄膜呈现出明显的各向异性。张应力诱导的各向异性与应力方向平行，而压应力形成垂直于应力方向的磁各向异性。各向异性场随应变的增大而线性增大。     

张应力对FeCoSiB非晶薄膜磁特性的影响

采用磁控溅射方法,在弯曲的玻璃基片上制备出受张应力作用的FeCoSiB非晶薄膜,研究了张应力大小对FeCoSiB薄膜的磁畴、矫顽力、剩磁、各向异性场等磁特性的影响.结果表明,薄膜的畴结构显著依赖于张应力,其磁畴宽度随张应力增加而增加;张应力导致FeCoSiB薄膜内形成较强的磁各向异性,其各向异性随应力的增大而增大.     

Influence of magnetic annealing on high-frequency magnetic properties of FeCoNd films

FeCoNd thin film with thickness of 166 nm has been fabricated on silicon (1 1 1) substrates by magnetron co-sputtering and annealed for one hour under magnetic field at different temperatures (T_a) from 200 °C to 700 °C. The As-deposited and annealed FeCoNd film samples at T_a ≤ 500 °C were amorphous while the ones obtained at T_a ≥ 600 °C were crystallized. We found that the perpendicular anisotropy field gradually decreases as the annealing temperature increases from room temperature to 300 °C. A well induced in-plane uniaxial anisotropy is achieved at the annealing temperature between 400 and 600 °C. The variation of the dynamic magnetic properties of annealed FeCoNd films can be well explained by the Landau-Lifshitz equation with the variation of the anisotropy field re-distribution and the damping constant upon magnetic annealing. The magnetic annealing might be a powerful post treatment method for high frequency application of magnetic thin films.     

Annealing behavior of magnetic anisotropy in CoNbZr films

The effect of magnetic and nonmagnetic annealing on the magnetic anisotropy in CoNbZr films, formed by a DC opposing-targets sputtering method, was investigated. It was revealed that the origin of the magnetic anisotropy is the directional ordering of the magnetic atoms. The anisotropy fields and the direction of the easy axis obtained when the films are annealed in zero magnetic field are almost the same as those for the magnetic field parallel to the easy axis of the as-deposited films. When the films are annealed in a magnetic field perpendicular to the easy axis, the anisotropy field induced in parallel with the magnetic field, H_k(t), is well represented by the following formula: ln {1-H_k(t )/H_k(∞)∝-√Tt, where H_k(∞) is the thermal equilibrium value of the anisotropy field and D is the diffusion constant. The activation energy of the as-deposited film is 0.86 eV. Annealing the film increases the activation energy which is 2.1 eV when the film is annealed at a temperature of 450°C for 2 h     

A new method for stress relieving amorphous alloys to improve magnetic properties

An analysis of the kinetics of stress relief annealing in amorphous alloys, with particular emphasis on the effect of annealing on the resulting magnetic properties, is made. Based on this analysis, an optimal procedure for annealing amorphous alloy magnetic cores is suggested. It involves a fast heatup to a high temperature for a short time. The expected benefits of this procedure are decreased embrittlement, lower strain induced anisotropy, and lower residual stresses. The conventional technique for stress relieving magnetic cores proved unsuitable for the application of the new annealing treatment. A new technique was devised in which the ribbon is dynamically annealed as it is wound onto the core. The magnetic properties of the resulting toroids are superior to those produced by the conventional technique.     

AlN/FeCoSiB磁电复合薄膜的制备及其逆磁电效应研究

借助射频磁控溅射成功制备了AlN/FeCoSiB磁电复合薄膜, 探讨了退火条件对AlN薄膜压电性能和FeCoSiB薄膜磁性能的影响, 并研究了其逆磁电响应。结果显示, 500℃退火处理的AlN薄膜具有高度(002)择优取向和柱状生长结构; 经过300℃退火后FeCoSiB薄膜的磁场灵敏度提高。该磁电复合薄膜的逆磁电电压系数(α_CME)在偏置磁场(H_dc)为875 A/m时达到最大值62.5 A/(m·V); 且磁感应强度(B)随交变电压(V_ac)的变化呈现优异的线性响应(线性度达到1.3%)。这种AlN/FeCoSiB磁电复合薄膜在磁场或电场探测领域具有广阔的应用前景。     

应力退火对Fe73.5Cu1Nb3Si13.5B9纳米晶合金磁性能的影响

采用一种新的退火方式,将Fe73．5Cu1Nb3Si13．5B9合金薄带在铜环上卷绕成铁芯,研究在这种方式的退火过程中Fe73．5Cu1Nb3Si13．5B9合金薄带晶化时产生的张应力对其磁性的影响．结果表明：与普通退火相比,这种张应力使退火后合金的剩磁Br明显下降（最低为0.22T）,形成的感生磁各向异性的易轴垂直于张应力的方向．这种横向感生磁各向异性起因于纳米bccFe（Si）晶粒内通过内应力和负的磁滞伸缩引起的磁弹性作用。     

张力退火感生各向异性对纳米晶合金磁性能的影响

对Fe_74.1Cu₁Nb₃Si₁₅B_6.9(%,原子分数)纳米晶合金进行连续张力退火,研究了张力退火感生各向异性对纳米晶合金磁性能的影响。结果表明,张力退火产生的感生各向异性常数(K_u)与退火张力(σ)满足线性关系。随着退火张力的增大合金在f =5 kHz和H=3 A/m测试点的有效磁导率(μ_e)先增大后减小,且随着磁场和频率的提高有效磁导率(μ_e)的衰减减小。退火张力为67 MPa时有效磁导率(μ_e)在磁场强度H为0~800 A/m和频率f为1 k~3 MHz范围内保持约800,表现出恒导磁特性。同时,合金的单位质量损耗(P_m)随着退火张力的增大而减小,当退火张力为67 MPa时损耗为68 W/kg (测试条件：B_m=300 mT,f =100 kHz),与无张力退火相比下降约67%。同时,通过磁光克尔效应观察到张力退火后合金内部形成垂直于张力方向的180°片形畴,随着退火张力的增大磁畴宽度减小且趋于一致,退火张力为67 MPa时片形畴的宽度约为85 μm。     

非晶FeSiB薄膜中的巨磁阻抗效应

采用射频溅射法在三组不同溅射条件下制备了FeSiB薄膜。测量了溅射薄膜的磁滞回线 ,并利用HP 41 94A阻抗分析仪 ,在 1～ 40MHz频率范围内研究了样品的巨磁阻抗效应。结果表明 :溅射条件对薄膜磁性能和巨磁阻抗效应影响很大 ,其中氩气压强为 6 65Pa ,磁场感生横向单轴磁各向异性的薄膜具有较好的软磁性能和较大的阻抗变化比值。一定温度下退火能够消除部分应力 ,阻抗变化的灵敏度能提高一倍。另外 ,对巨磁阻抗效应与测量磁场和薄膜易轴的相对位置取向之间的关系也作了讨论     

Effects of MgO and MgO/Pd seed-layers on perpendicular magnetic anisotropy of CoPd thin films

We studied the effects of MgO and MgO/Pd seed-layers on perpendicular magnetic anisotropy in co-sputtered CoPd films. CoPd films with the MgO seed-layer showed perpendicular magnetic properties that were superior to those with another after annealing. The loop squareness was unity, indicating strong perpendicular magnetic anisotropy, when the MgO seed-layer was thicker than 2 nm. We observed that the out-of-plane CoPd (111) texture was strongly developed, as well as the in-plane tensile stress in the CoPd films. The magnetoelastic anisotropy coming from a negative magnetostriction λ₁₁₁ under the in-plane tensile stress dominating over other anisotropies is likely responsible for creating such strong perpendicular magnetic anisotropy. In the case of the MgO/Pd seed-layer, the CoPd films showed mixed anisotropy having both in-plane and out-of-plane magnetic anisotropy components after annealing. The appearance of the strong (100) texture of the CoPd films with the MgO/Pd seed-layer is believed to have caused the decrease in the perpendicular magnetic anisotropy that originated from the magnetoelastic anisotropy due to the additional contribution from the positive magnetostriction λ₁₀₀ but less contribution from the negative magnetostriction λ₁₁₁ when the CoPd films are under in-plane tensile stress.     

Magnetic and structural properties of ion beam sputtered Fe-Zr-Nb-B-Cu thin films

Magnetic and structural properties of Fe-Zr-Nb-B-Cu thin films, prepared by ion beam sputtering on silicon substrates by using a target made up of amorphous ribbons of nominal composition Fe₈₄Zr_3.5Nb_3.5B₈Cu₁, are reported. As-deposited thin film samples exhibit an in-plane uniaxial anisotropy, which can be ascribed to the preparation technique and the coupling of quenched-in internal stresses. Structural measurements indicate no significant variation of the grain size with thickness and with the annealing temperature. Increase in surface irregularities with annealing temperature and oxidation results in aggregates that would act as pinning centers, affecting the magnetic properties leading to magnetic hardening of the specimens. The role of the magnetic anisotropy is thoroughly discussed with the help of magnetic and ferromagnetic resonance measurements.     

Crystal structure and magnetic properties of Permalloy filmssputtered by mixed Ar-N2 gases

The crystallographic and magnetic properties of 1-μm-thick Permalloy films sputtered by mixed argon and nitrogen gases have been investigated. These films are composed of (111) textured grains of face-centered cubic and (002) textured grains of body-centered tetragonal which are deformed from face-centered cubic. Adding nitrogen to argon gas increases the amount of (002) textured grains and lattice strain. The anisotropy field of these films is smaller than that of films sputtered by pure argon. The coercive force of films containing relatively large amounts of nitrogen increases with annealing. The coercive force of the annealed films is correlated with a change in the lattice constant of the face-centered cubic grains. The magnetocrystalline anisotropy of these grains is likely to be one of the causes of perpendicular anisotropy     

Si含量对纳米晶Fe_(87-x)Cu_1Nb_3Si_xB_9合金磁性能的影响

研究了Si含量对Fe87-xCu1Nb3SixB9合金经不同方式退火后磁性能的影响。结果表明:随Si含量的增加,Fe87-xCu1Nb3SixB9合金经普通退火后软磁性能逐渐得到优化;经磁退火后可感生出单轴磁各向异性,且磁退火特征随Si含量的增加而逐渐明显。根据横磁退火实验结果计算出的感生磁各向异性值Ku,则由26.7J/m3(Si=9.5at%)降低至14.1J/m3(Si=13.5at%)。由实验数据的分析认为Fe87-xCu1Nb3SixB9合金在高Si含量时经普通退火或纵磁退火后呈现优异的软磁特性,归因于析出的α-Fe(Si)相晶粒具有小的磁晶各向异性K1,从而导致合金具有更低的有效磁各向异性常数K所至。     

Magnetic properties of evaporated CoCr films

Perpendicular magnetic CoCr films were prepared on glass substrates using electron beam evaporation. The magnetic properties depend strongly on the substrate temperature, Ts. The anisotropy field,H_{k}^{eff}, and the perpendicular coercivity, Hc(perp) show maximum values at Tsaround 250°C. In this case, the alignment of c-axis is optimal and the grain size is smallest. The lattice spacing of the c-planes increases wlth Tsuntil 300°C. When the films prepared below 200°C were annealed around 300°C in high vacuum, the saturation magnetization, Ms, increased. The value of Ms, however, decrease by annealing above 400°C. In spite of the decrease of Msdue to the annealing above 400°C,H_{k}^{eff}and Hc(perp) increase by annealing above 400°C. If the films were bombarded by argon ions during film growth, Msdecreased and the internal stress changed from tensile to compressive. For low substrate temperature (below 150°C),H_{k}^{eff}decreased due to ion bombardment.     

Low temperature ordering of FePt films by in-situ heating deposition plus post deposition annealing

FePt thin films with 40 nm thickness were prepared on thermally oxidized Si (001) substrates by dc magnetron sputtering at the nominal growth temperature 375 °C. The effects of annealing on microstructure and magnetic properties of FePt thin films were investigated. The as-deposited FePt thin films show soft magnetic properties. After the as-deposited FePt thin films were annealed at various temperatures and furnace cooled, it is found that the ordering temperature of L1₀ FePt phase could be reduced to 350 °C. For FePt thin films annealed at 350 °C, the in-plane and out-of-plane coercivities of the films increased to 510 and 543 kA/m, respectively, and the films had hard magnetic properties. A highly (001) orientation was obtained, when FePt thin films were annealed at 600 °C. And the hysteresis loops of FePt thin films annealed at 600 °C show out-of-plane magnetic anisotropy.     

Tensile mechanical behaviour of quenched and annealed isotactic polypropylene films over a wide range of strain rates

The tensile mechanical behaviour of quenched and annealed isotactic polypropylene (iPP) films has been analysed over a wide range of strain rates, i.e. from 10^–3 to 3×10⁺²s^–1. Evolution of mechanical properties of such films versus strain rate has been analysed through the microstructure. Thus, both the Young's modulus and the yield stress could be mainly controlled not only by the crystallinity ratio but also by the physical cross-linking degree of the amorphous phase induced by crystalline entities. For a given crystallinity ratio, the drawability of quenched and annealed iPP films is mainly controlled by the sum of the effects induced by both the physical cross-linking degree of the amorphous phase and the perfection degree of the crystalline phase. The increase in annealing temperature leads to the opposite evolution of these two microstructural parameters and then to opposite effects on the drawability of films. Changes in original microstructure of quenched films induced by drawing at various draw ratios and at various strain rates are also discussed.     

溅射气压对FeCoSiB非晶薄膜表面形貌及磁特性的影响

利用磁控溅射的方法，在玻璃基片上制备了FeCoSiB非晶薄膜，研究了溅射心气压强对薄膜表面形貌及磁特性的影响。结果表明，薄膜的表面形貌显著依赖于心气压强，随着山Ar压强的增加，薄膜表面颗粒增大，粗糙度增加并形成柱状微结构。心气压强对薄膜磁特性有显著的影响，随血压强增加，薄膜的矫顽力增加，而剩磁则呈下降趋势。从薄膜的磁滞回线、矫顽力以及剩磁随溅射气压的变化规律可知，溅射气压较小时制备的薄膜软磁性能较好．     

Thickness dependence of microstructures and magnetic properties for CoPt/Ag nanocomposite thin films

Ag underlayer (30 nm) has improved the degree of ordering and perpendicular magnetic anisotropy of CoPt films (7.5-10 nm). After annealing at 600 °C and 700 °C, the perpendicular coercivity of CoPt/Ag films has been raised as the thicknesses of CoPt layers are increased. The magnetic easy axis of CoPt/Ag films would change from a random orientation to an out-of-plane orientation. It is found that Ag underlayer with thickness of 30 nm can improve the perpendicular magnetic properties of CoPt layers with thicknesses in the range of 7.5-10 nm. The CoPt/Ag films would be a candidate for perpendicular magnetic recording media.     

低温应力退火Fe基合金薄带巨磁阻抗特性的研究

通过同步辐射X射线衍射技术,观测Fe73.5Cu1Nb3Si13.5B9非晶薄带经过不同温度和不同应力退火60 min后样品的微观结构,利用HP4294A型阻抗分析仪测量相应样品的巨磁阻抗比与磁各向异性。研究结果表明,在450℃下施加不同应力退火的样品仍然处于非晶结构状态,并且在应力为112.1 MPa的条件下产生优异的磁性能,样品的最大巨磁阻抗比达到了1818.7%,是自由退火条件下最大巨磁阻抗比的1.9倍,同时能够改变巨磁阻抗曲线的形状,使Fe基合金薄带的巨磁阻抗曲线具有宽线性的特性。对实验数据进行拟合后发现,样品的最大巨磁阻抗比和磁各向异性场与外加应力都具有线性关系,磁感灵敏度与外加应力具有负指数关系。通过探究发现具有非晶结构的Fe基合金薄带的磁学性能对应力敏感,可以作为研究非晶纳米晶合金材料应力敏感问题的另一个新方向。     

Induced anisotropy in Ni-Fe films

A survey of experimental results for magnetic anisotropy induced during evaporation and annealing of polycrystalline Ni-Fe alloy films is given. Existing data for the uniaxial anisotropy constantKappear to be bounded from above by the combined predictions of strain and directional-ordering theories. The strain anisotropy frequently attains theoretical values, and often less, while directional-ordering anisotropy in high-vacuum films (circa 10^-5torr) generally attains half or less of theoretical expectations.