High frequency magnetic properties and intergranule interaction of nano-granular films with high resistivity and high permeability

In order to get magnetic films with high permeability and high resistivity for applications in high frequency devices, (Fe65Co35)x(SiO2)1-x nano-granular films with low metal volume fraction were fabricated by radio frequency magnetron sputtering, and excellent soft magnetic properties have been acquired by annealing the sample with x = 0.38 at 260 degrees C in a magnetic field. The real part micro' of complex permeability is larger than 100 when frequency f is lower than 0.7 GHz, and the ferromagnetic resonance frequency f(r) is as high as 1.8 GHz. More interestedly, the resistivity of this sample reaches 13.4 momega x cm, 4 orders higher than that of pure FeCo alloy. Ferromagnetic resonance experiment and deltam-H curve study were employed to elucidate the mechanism of soft magnetic properties. The results reveal that the intergranule exchange coupling plays an important role in realizing good soft magnetic properties for metal-insulator granular films.     

Fe-O纳米晶合金膜的软磁和高频特性(英文)

采用等离子体增强射频磁控溅射沉积方法,在室温下制备了Fe-O合金薄膜.研究了氧的掺杂量和薄膜厚度对薄膜软磁和高频特性的影响.结果发现少量氧的掺杂不导致低饱和磁化强度铁氧化物的形成,但可使薄膜晶粒细化,矫顽力下降.在薄膜厚度低于150 nm且氧气与氩气相对流量比为2.4%的条件下,薄膜的实部磁导率高达1100且能够维持到1GHz.     

NiO/FeCo磁性多层膜的高频磁性

制备了一系列具有铁磁/反铁磁交换偏置作用的[NiO/Fe65Co35]10多层膜,使用振动样品磁强计(VSM)测量了样品的静磁参数,利用微带线法测量了样品4GHz-10GHz的磁谱,首次制备并测得了自然共振频率(fr)在6GHz以上,最高到fr=9.6GHz的薄膜样品。结果表明交换偏置场(Hex)、各向异性场(Hua)、以及矫顽力(Hc)随铁磁层厚度(tFM)增大而减小;基于Landau-Lifishitz(L-L)方程对静磁参量和磁谱进行了比较,发现样品自然共振频率较L-L方程计算值偏大30%以上。     

Cluster-assembled Tb-Fe nanostructured films produced by low energy cluster beam deposition

Cluster-assembled Tb-Fe nanostructured films were prepared by the low energy cluster beam deposition method. The microstructure, magnetization and magnetostriction were investigated for the films. It is shown that the film is assembled by monodisperse spherical nanoparticles with average diameter of ～30?nm which are distributed uniformly. The cluster-assembled Tb-Fe nanostructured films exhibit good magnetization and possess giant magnetostriction with saturation value of ～1060 × 10(-6), much higher than that of the common Tb-Fe films. The origin of good magnetization and giant magnetostriction for the cluster-assembled Tb-Fe nanostructured film was discussed. The present work opens a new avenue to produce the nanostructured magnetostrictive alloy in application of a nano-electro-mechanical system.     

纳米磁性颗粒膜（Fe65Co35）x（SiO2）1-x的微结构和磁性

用射频磁控溅射制备了由FeCo纳米磁性颗粒分布在SiO2绝缘介质中形成的（Fe65Co35）0.4（2SiO2）0.58纳米颗粒膜。通过低温磁场回火得到很好的软磁性,易轴矫顽力低至143Am^-1;并呈现很好的面内单轴磁各向异性,各向异性场为3820Am^-1;电阻率高达13.4mΩ·cm。样品的磁谱（磁导率与频率的关系）显示出很好的高频特性：在工作频率f〈0.7GHz时,复数磁导率的实部μ′〉100,FMR频率达1.8GHz,说明样品有高的截止频率,显示出在高频器件及抗电磁干扰技术方面具有很好的应用前景。用铁磁共振实验证明此样品中好的高频软磁性是由于实现了颗粒间的铁磁性交换耦合所致。     

Permeability measurement in the GHz range for soft-magnetic filmusing the M/C/M inductance-line

This work reports a new technique for measuring permeability of magnetic alloy films above 1 GHz by using an inductance-line, which has a magnetic alloy films(M)/conductor(C)/magnetic alloy films(M) stacked structure and is installed in a microstrip circuit. The imaginary part of the relative permeability μ_r" was estimated from the magnetic absorption in the M/C/M inductance-line, by analyzing its transmission characteristics. The Kramers-Kronig relation was used for the transformation from μ_r" to the real part μ_r '. Complex relative permeability was measured in the 1 MHz-20 GHz frequency range for NiFe-SiO₂, CoZrNb-SiO₂ and CoFe-SiO₂ multilayer films. The μ_r-f characteristics, static relative permeability μ_r"(0) and ferromagnetic resonance frequency f_k values were confirmed to agree with those obtained by the conventional M/C/M technique and by calculation     

高致密度FeNi纳米颗粒薄膜制备与性能研究

传统磁控溅射装置制备的纳米颗粒薄膜粒径不均一并且实现粒径大小调控比较困难.本研究采用电场辅助沉积技术,在沉积平台施加5～30 kV的电场,以Si(100)为衬底制备了一系列纳米颗粒粒径均一的高致密度FeNi纳米颗粒薄膜材料.通过XRD、SEM以及VSM测量,研究了不同沉积电场下FeNi纳米颗粒薄膜的结构、形貌和磁性能....     

SmCo/FeCo/SmCo三层膜中的剩磁增强效应

系统地研究了磁控溅射制备的Sm22Co78/Fe65Co35/Sm22Co78三层膜系统中，当软磁相的体积分数一定时，矫顽力和剩磁比随FeCo软磁层厚度（d)的变化，所有样品的磁滞回线均为单一硬磁相特征：说明FeCo软磁层与SmCo硬磁层之间的交换相互作用，使两相很好地复合在一起。当软磁相的体积分数为15％，20％，30％的情况下，矫顽力随d的变化都出现峰值，而剩磁比则单调增加，当体积分数为50％时，矫顽力随d的增加滑有峰值，但剩磁比还是单调增加，随着软磁体积分数的增加，矫顽力峰值及峰值位置都是单调减少。     

V部分替代Nb对含Co FINEMET型合金磁性的影响

研究了含Co的Finemet型（Fe.．5Co0．5）73．5Nb3Si13．5B9Cu1和（Fe0.5Co0．5）73．5Nb2V1Si13．5B9Cu1合金在不同温度纳米晶化后的磁性．结果表明,用V部分替代Nb对淬态（Fe0.5Co0．5）73．5Nb2V1Si13.5B9Cu1非晶合金的居里温度没有明显的影响,但是形成（Fe0．5Co0．5）7a．5Nb2V1Si13．589Cu1纳米晶合金使剩余非晶中Co的含量降低,导致初始磁导率在高温下快速衰减;用V部分替代Nb使（Fe0．5Co0.5）73．5Nb2ViSi13．5B9Cu1纳米晶合金中的晶体相含有更多的Co,增大了材料的饱和磁感应强度B8并显著提高了初始磁导率．     

Interaction Effects in SmCo/FeCo Bilayer Film Media

The magnetic property of Sm22Co78/Fe65Co35 bilayer film media prepared by magnetron sputtering was measured. All the samples have in-plane anisotropy and the hysteresis loops are simple single loops, indicating that the two phases are strongly exchange-coupled. The reduced remanence (Mr/Ms) was found to increase from 0.58 to 0.8 with increasing Fe65Co35 layer thickness (d) for a fixed Sm22Co78 layer thickness. The coercivity was found to increase with increasing a few Fe65Co35 layer, and then to decrease with continuously increasing Fe65Cos5 layer. The intergranular exchange and magnetostatic interaction effects were measured from their remanence magnetization curves.     

Electronic properties and applications of cluster-assembled carbon films

Nanostructured carbon thin films can be grown by deposition of cluster beams produced in supersonic expansions. By using a pulsed microplasma cluster source and by exploiting aerodynamic focusing effects typical of supersonic expansions, the structure and the properties of the films can be controlled by varying the cluster mass distribution prior to deposition. Nanocomposite films can be produced by co-depositing carbon clusters and metallic nanoparticles. The films have been characterized by various spectroscopic techniques and tested in view of applications for field emission, supercapacitors, gas sensing. The possibility of patterning cluster-assembled carbon films by shadow masking or by ultraviolet photon irradiation suggests interesting perspective for the integration of nanostructured carbon films on microfabricated devices and for the production of components for an all-carbon electronics.     

Growth, structure, and properties of BiFeO3/-BiCrO3 films obtained by dual cross beam PLD

The properties of epitaxial Bi(2)FeCrO(6) thin films, recently synthesized by pulsed laser deposition, have partially confirmed the theoretical predictions (i.e., a magnetic moment of 2 micro(B) per formula unit and a polarization of approximately 80 microC/cm(2) at 0 K). The existence of magnetic ordering at room temperature for this material is an unexpected, but very promising, result that needs to be further investigated. Because magnetism is assumed to arise from the exchange interaction between the Fe and Cr cations, the magnetic behavior is strongly dependent on both their ordering and the distance between them. We present here the successful synthesis of epitaxial Bi(2)Fe(x)CryO(6) (BFCO x/y) films grown on SrTiO3 substrates using dual crossed-beam, pulsed-laser deposition. The crystal structure of the films has different types of (111)-oriented superstructures, depending on the deposition conditions. The multiferroic character of BFCO (x/y) films is proven by the presence of both ferroelectric and magnetic hysteresis at room temperature. The oxidation state of Fe and Cr ions in the films is shown to be 3+ only, and the difference in macroscopic magnetization with Fe/Cr ratio composition could only be due to ordering of the Cr(3+) and Fe(3+) cations to the modification of the exchange interaction between them.     

Temperature Dependence of Magnetic Properties of SmCo/FeCo Multilayer Films

1. IntroductionIn addition to the magnetic properties of each individual particle, intergrain illteraction play a dominantrole during demagnetization processes[1'2]. These intergrain interactions are sensitively influenced by intergranular phases depending on the respective preparation methodl3'4]. A systematic improvement of permanent magnets is only possible by a deeper understanding of the relations between intergrain interaction, microstructural features, and magnetic properties.In this pa…     

Structure and magnetic properties of Co/CoO and Co/Si core–shell cluster assemblies prepared via gas-phase

Plasma-gas condensation cluster deposition systems have been introduced and applied for preparation of Co/CoO and Co/Si clusters assemblies. In Co/CoO cluster assemblies prepared by the single source PGC system with introduction of O₂ gas into the deposition chamber, fcc Co cores are covered with NaCl type CoO shells, showing marked enhancement of unidirectional and uniaxial magnetic anisotropy and a clear cross-over phenomenon in the magnetic relaxation from the high temperature thermal regime to the low temperarure quantum tunneling regime. In Co/Si cluster assemblies prepared by the double source PGC system, fcc Co cores are also covered with amorphous Si rich shells, showing rather small magnetic coercivity. Since Co/CoO and Co/Si core–shell clusters are stable in ambient atmosphere, they will be used as building blocks for novel nano-structure-controlled materials.     

Carbon additive effects on the nanostructure and magnetic property of the Co-Fe-Zr-B-C films

In this study, the carbon additive Co-Fe-Zr-B alloy films were prepared by dual-gun co-sputtering. The effects of the carbon addition and heat treatment on the nanostructure and magnetic properties of the Co-Fe-Zr-B-C alloy films are reported. The experimental results show that a crystalline (Co, Fe) phase formed after heat treatment at 400 in the Co-Fe-Zr-B-C films with low carbon additive level. Carbon atoms inhibited the crystallization of the as-deposited Co-Fe-Zr-B-C films. From the TEM observation, the nanostructures, such as the atomic structure and grain sizes, showed a strong carbon content dependence. The coercivities of the Co-Fe-Zr-B-C films annealed at 400 varied from 18 to 0.3 Oe with the increasing carbon addition. However, the films annealed at higher temperature exhibited a dramatic increase in the coercivities, which correlated to the formation of the crystalline (Co, Fe) phase. The resistivities of the Co-Fe-Zr-B-C films relied on the carbon contents rather than on annealing temperatures.     

Influence of different conducting substrates on magnetic properties of electrodeposited Ni–Fe thin films

Electrodeposition of Ni–Fe soft magnetic alloy on copper and stainless steel substrates was performed in chloride bath. The deposition parameters such as current density, pH, temperature and deposition time have been investigated. From the investigation the optimized deposition parameters were current density 3.5 mA/cm², pH 3, temperature 30 °C and deposition time 15 min. The Ni–Fe magnetic alloys deposited on copper and stainless steel substrates under optimized deposition parameters are subjected to various characterizations. The structural and surface morphology of the Ni–Fe films were detected by using X-ray diffractogram (XRD) and scanning electron microscope (SEM) respectively. The constituents in the films were determined by energy dispersive X-ray spectroscopy (EDAX) technique. The magnetic properties such as the coercivity (H_c) and saturation magnetization of the films were studied with the help of vibrating sample magnetometer (VSM). From the magnetic studies it is concluded that the grain size are create a considerable impact on magnetic behavior of the films on both the substrates. The films prepared on stainless steel substrate of 0.1 M concentration at optimized deposition parameters exhibits higher coercivity (5010 Oe) which seems to be ideal for magnetic sensor applications.     

退火处理Fe(Co)Al(Zr)O系薄膜磁性能的研究

采用射频磁控溅射装置在氩气氛下制备了Fe(Co)Al(Zr)O系薄膜.用X射线衍射仪、透射电镜及其选区衍射来分析薄膜的微结构.用振动样品磁强计、磁导计等测量了矫顽力Hc、饱和磁化强度Ms及磁导率等磁性参数.通过退火处理研究了Fe(Co)Al(Zr)O系薄膜的磁性能.Fe(Co)Al(Zr)O系薄膜磁各向异性是由形状各向异性引起的.     

溅射——气体——聚集共沉积法制备金属／金属（介质）复合团簇镶嵌薄膜

提出了溅射－气体－聚集共沉积制备金属／金属（介质）复合团簇镶嵌薄膜的新方法，并利用该方法成功地在方华膜衬底上制备了系列Ｆｅ／Ａｇ及ＣａＦ２复合团簇镶嵌薄膜样品。透射电镜分析结果表明，样品中Ｆｅ（Ｃｕ）团簇都较好地镶嵌于Ａｇ（ＣａＦ２）基质中，其结构为两种材料的多晶共存形态。进一步分析发现，与块材相比，Ｆｅ／Ａｇ样品中Ｆｅ团簇晶格常数呈现出不同程度的收缩，而Ｃｕ／ＣａＦ２样品中Ｃｕ团簇晶格常数则呈现出不同程度的膨胀。运用附加压力的模型对该现象进行了解释。     

The composition,structure and optical properties of weakly magnetic Co-containing amorphous Si and Ge films

This study investigated the composition, structure and optical properties of amorphous SiCo and GeCo films. The samples were prepared by radio frequency sputtering. Films were deposited with Co atomic concentrations in the range of 1.7–10.3 at.%. After deposition, the films were submitted to thermal treatments up to 900 °C and investigated by energy dispersive X-ray spectrometry, X-ray diffraction, Raman scattering and optical transmission spectroscopy. Additionally, magnetic force microscopy measurements were performed at room temperature. For comparison purposes, Co-free samples were also prepared, annealed and characterized following a similar procedure. The experimental results indicated the following: (1) the Co atoms were effectively and homogeneously incorporated into the amorphous hosts; (2) the as-deposited films (either pure or containing Co) were essentially amorphous; (3) annealing the films at high temperatures induced crystallization; (4) after crystallization, non-magnetic CoSi₂ (silicide) and CoGe₂ (germanide) phases were identified in the Co-containing Si and Ge films, respectively; (5) the optical properties of the films were significantly affected by the insertion of Co and by the annealing temperature; and (6) the samples exhibited a reduced magnetic signal at room temperature. These experimental observations were systematically studied, which are presented and discussed in this report.     

Controlled synthesis of core-shell iron-silica nanoparticles and their magneto-dielectric properties in polymer composites

Low loss core-shell iron-silica nanocomposites with improved magneto-dielectric properties at radio frequencies (1 MHz-1 GHz) were successfully fabricated. A new simple method was developed to synthesize metallic iron (Fe) nanoparticles with uniform size distribution in an aqueous environment at room temperature. Citric acid and oleic acid served as surface-capping agents to control the particle size of the synthesized Fe nanoparticles. Smaller Fe nanoparticles with narrower particle size distribution were obtained as the concentration ratio of iron ions to carboxylic acid groups decreased. The Fe nanoparticles were subsequently coated with silica (SiO(2)) layers to prevent the iron cores oxidizing. Polymer composites were prepared by incorporating Fe@SiO(2) nanoparticles with polydimethylsiloxane (PDMS) elastomers. Experimental results showed that the dielectric permittivity (ε) and magnetic permeability (μ) of the polymer composite increased with increasing amount of Fe@SiO(2) nanoparticle doping. The dielectric loss (tanδ) was near 0.020 at a frequency of 1 GHz.