NiCuZn铁氧体的偏置特性及温度稳定性研究

采用传统陶瓷制备工艺制备了NiCuZn铁氧体材料。研究了V2O5、MoO3掺杂对NiCuZn铁氧体材料的微观形貌、直流叠加性能、温度稳定性的影响。研究表明,适量添加V2O5、MoO3可增加铁氧体材料晶界非磁性相的厚度,提高退磁场Hd;从而降低铁氧体材料的磁导率在直流叠加磁场作用下的下降速度。适量添加V2O5、MoO3可调整材料的晶粒尺寸及气孔、晶界等非磁性相的含量;进而改变饱和磁化强度、磁各向异性场、退磁场对材料磁导率的影响权重,最终达到调整材料温度系数的目的。     

V_2O_5掺杂改善锰锌铁氧体组织及性能的研究

采用传统陶瓷法制备锰锌铁氧体,研究了不同V_2O_5掺杂量对锰锌铁氧体烧结试样微观结构及磁性能的影响。获得了适用于电磁加热的高性能Mn Zn铁氧体材料。结果表明,适量的掺杂V_2O_5能显著改善材料的微观结构,并且能明显提高材料的磁性能。当V_2O_5掺杂量为质量分数0.05%时,样品拥有最佳的磁性能,其振幅磁导率、比总损耗及矫顽力分别为1704,30.36 W/kg,4.8 A/m(100 m T,100 k Hz)。     

特高频高磁损耗材料的制备及其磁特性研究

采用磁粉芯工艺制备了抑制电磁干扰(EMI)用高磁损耗软磁合金复合材料(SCM)。通过SEM微观形貌观察与复磁导率(μr'、μr')测试,对不同制备阶段的样品进行了分析,研究了球磨与退火过程对磁导率的影响,并与铁氧体材料磁导率特性进行了对比。结果表明:μr'呈磁共振双峰宽频分布,1.2GHz时,μr'为7.3,μr'max为14.5。特高频带内,SCM磁损耗性能超过铁氧体材料。     

H_3BO_3掺杂对Co_2Z基磁介天线基板材料影响研究

为研制适用于915 MHz RFID天线小型化应用需要的磁介基板材料,采用固相反应烧结法研究了H3BO3掺杂对(Ba0.5Sr0.5)3Co2Fe24O41铁氧体微观形貌和磁介性能的影响。通过研究发现,H3BO3掺杂能很好地促进Co2Z铁氧体的低温烧结成相。同时,H3BO3掺杂也有利于抑制Co2Z铁氧体晶粒生长。随着H3BO3掺杂量的增多,材料体系的磁导率持续下降,而介电常数先上升后下降。当掺杂H3BO3的质量分数为4%,材料体系在915MHz时可获得磁导率为2.45,介电常数为10.41,磁损耗正切为0.057,介电损耗正切为0.005的综合磁介性能。     

采用超磁致伸缩薄膜的光纤磁场传感器

采用马赫-曾德尔干涉仪,对TbDyFe超磁致伸缩薄膜/光纤传感器的磁探测性能进行了实验测试.结果表明:在1 kHz调制频率附近,传感器对磁场具有最大的信号响应;在恒定直流磁场及调制磁场强度小于1 kA/m的条件下,系统输出信号大小随调制磁场强度线性增加;在35～50 kA/m的直流磁场范围内,传感器可探测的最小磁场变化为8.6×10-2A/m.     

频率和幅度双可调铁氧体LTCC衰减器

电路小型化需要多频段可调元器件,基于CPW(共面波导)结构采用最新的铁氧体LTCC(低温共烧陶瓷)技术,内埋若干偏置线圈以产生内部偏置磁场,调节线圈内电流大小以控制偏置磁场大小,从而控制衰减器的工作频率,同时,控制通电线圈的个数以改变衰减器的衰减幅度,进而实现频率和衰减幅度双可调的衰减器。首先介绍了基于铁氧体材料的衰减器基本原理,然后展示了基于铁氧体LTCC 技术的无内置线圈衰减器的设计、制作和测量,在外加偏置磁场的条件下,验证了铁氧体LTCC 衰减器的理论可行性,经实测,该衰减器可以在4～9 GHz之间实现频率可调以及相应的衰减幅度可调。随后提出了有内置线圈的铁氧体LTCC 衰减器模型,并展示了线圈静态磁场、衰减器频率可调和幅度可调的仿真结果。最后制作了该衰减器并完成了实测,在铁氧体LTCC特有内部衰减场上实现了频率和幅度双可调衰减器,从而给出了可调衰减器的新思路。     

线性和非线性静磁表面波能流的受控偏转特性

针对波矢Ｋ与外偏置磁场Ｈ０成任意角度的静磁表面波提出了传播截止角的概念，给出了依赖于强度的非线性色散方程，研究揭示了线性和非线性静磁表面波能流方向受Ｈ０方向控制在０～９０°范围内可调的特性。     

无线充电和近场通信兼用贫铁MnZn铁氧体材料

采用传统的陶瓷工艺制备贫铁MnZn铁氧体材料Mn0.61Zn0.41Ti0.02Fe1.96O4,并采用流延工艺制备出厚度为100~150μm的贫铁MnZn铁氧体薄片。研究了贫铁MnZn铁氧体材料的微观形貌和晶相结构,测试了贫铁MnZn铁氧体材料的磁性能。研究表明,贫铁Mn Zn铁氧体在低频区域的磁性能与富铁MnZn铁氧体相当,并在13.56 MHz的高频区域仍保持了较高的磁导率。通过运用仿真软件CST模拟NFC(近场通信)天线的场强分布并根据可读写距离测试了铁氧体薄片的屏蔽能力,讨论了贫铁MnZn铁氧体材料同时运用于无线充电及近场通信的可行性。     

加工表面损伤对软磁铁氧体磁性能的影响

一.引言软磁铁氧体材料广泛用于VTR和计算机外部存贮器磁头中。由于它的电阻率为1～10~(12)Ω·m,比软磁合金高得多,高频损耗低,并且,高频时仍具有较高的初始磁导率(μ_5MH_2>500)。因此,软磁铁氧体在VTR和计算机外部存贮器磁头领域里占有重要地位。随着记录密度的不断提高,对磁头材料的磁性能的要求也愈高。用于磁头中的软磁铁氧体要具有高的最大磁导率,以减小记录磁头的输入功率,增     

Co-Ti替代钡铁氧体的高频磁性研究

用化学共沉淀工艺制备了Co-Ti替代系列钡铁氧体磁粉及烧结磁体,结合相结构、显微形貌分析和对材料磁化机理的讨论,该文主要研究了替代量和烧结温度对钡铁氧体高频磁性的影响。实验表明,初始磁导率和共振频率随替代量的变化存在极值,当Co-Ti替代量为1.0时钡铁氧体具有较高的磁导率和较低的磁共振频率,偏离1.0均导致磁导率的降低和磁共振频率的升高;高烧结温度导致晶粒尺寸的长大和晶格结构的完善,有利于提高材料的磁导率,同时降低了磁共振频率。     

可调谐微机电电感(续)(英文)

<正>3 Magnetic Core Tuned Inductor Magnetic core tuned inductor is tuned based on the magneto impedance effect[32].As the bias DC magnetic field is applied along to the axis of the inductor body,the transverse permeability of the soft magnetic layer can be changed to achieve the tunability of the inductance.In order to design tunable microinductors for microwave communication systems,such as the frequency range over 1 GHz,     

Electronically tunable magnetic patch antennas with metal magnetic films

AS new type of electronically tunable magnetic patch antennas with metal magnetic films was designed, fabricated, and tested at 2.1 GHz. The magnetic patch antennas showed an enhanced bandwidth of 50% over the non-magnetic patch antennas, a significantly enhanced directivity, and a large tunability of the radiation intensity of 4.23 dB at a low applied magnetic field of ~20 Oe     

High Power,Frequency Tunable,Submillimeter Wave ESR Device Using a Gyrotron as a Radiation Source

ESR device using a submillimeter wave gyrotron as a radiation source and a pulse magnet for high field up to 30 T has been constructed. Our gyrotrons (Gyrotron FU series) were developed as millimeter and submillimeter wave radiation sources and have attractive advantages for ESR spectroscopy, for example, high power and frequency tunability over broad range. The ESR device has been successfully applied to three cases of ESR measurements. In the first case, the temperature dependence of ESR was measured for a typical antiferromagnetic material MnO at the frequency of 301 GHz. In the second case, the dependence of the fine structure constant of the ruby on the magnetic field intensity was measured in the millimeter to submillimeter wave region. In these two cases, the gyrotron was operated by complete cw mode. In the final case, a pulse technique was applied to the ESR, the gyrotron was operated in pulse mode and the pulsed magnetic field was generated in the synchronized phase with the gyrotron operation.     

Conceptual Design Study of a Novel Gyrotron for NMR/DNP Spectroscopy

In this paper we present some initial results from a conceptual design study focused on the development of a novel frequency tunable gyrotron for nuclear magnetic resonance (NMR) spectroscopy with signal enhancement based on the utilization of high field radiation and dynamic nuclear polarization (DNP) technique. The first variants of both the electron optical system and the resonant cavity which have been designed aiming continuous frequency tunability in a broad frequency band are presented and discussed. The selected method for frequency tunability is based on the excitation of higher order axial modes and smooth transition between them. It was selected after a critical examination of the known theoretical and practical results related to the frequency control in gyrotrons. It is believed that the current conceptual design is an appropriate basis for development of the next (optimized) design which will include also a detailed design of other components (mode converter, output window etc.) and magnetic circuit (superconducting magnet and supplementary solenoids) as well as for the overall mechanical design and fabrication of the prospective gyrotron.     

Magnetically tunable microstrip resonator based on polycrystallineferrite

A conventional microstrip ring resonator consisting of a polycrystalline ferrite substrate is demonstrated. This resonator produces improved tunability compared with other available versions. Resonators with tunability approaching 31% at a minimum insertion loss of 11.17 dB in a magnetic field of 3 kG applied longitudinally along wave propagation have been demonstrated using LiZiTi ferrite composition. Tunability of 31% is the best reported for any tunable structure     

低频脉冲磁场中磁屏蔽体磁饱和效应的试验研究

针对磁屏蔽体在低频脉冲磁场环境中可能存在的磁饱和问题，利用试验方法开展了磁饱和效应研究，证实了常规工程屏蔽体可在低频脉冲磁场环境中达到磁饱和状态，并通过观测屏蔽效能的变化获得了磁饱和规律，同时分析了磁饱和效应对屏蔽效能的影响及其与屏蔽体的材料磁导率、壳体厚度、外形尺寸等参数的关系. 研究表明:磁屏蔽体屏蔽效能在磁饱和效应影响下，呈现出明显的动态变化特点，具有与屏蔽壳体磁导率类似的变化趋势；壳体厚度2 mm以内、长宽高为2 m×2 m×2 m左右的屏蔽体在上升时间为300 μs、持续时间为1.2 ms的磁场环境中，达到磁饱和状态的磁化场强度约为10 mT，其磁饱和难易程度与磁导率及外形尺寸负相关，与壳体厚度正相关. 试验研究结果与理论分析结论一致，可为磁屏蔽体的科学合理设计提供参考，具有较高的工程应用价值.     

Electrically tunable microwave filters based on ferromagnetic resonance in ferrite-ferroelectric bilayers

The design and analysis of a new class of electric field-tunable ferrite-ferroelectric microwave bandpass filter is discussed. The tunability is possible through magnetoelectric interactions. When the composite is subjected to an electric field, the mechanical deformation due to piezoelectric effect manifests as a magnetic field shift in the ferromagnetic resonance for the ferrite. The electrical tuning is much faster than traditional magnetic tuning and has practically zero power consumption.     

Dual-tunable hybrid wave ferrite-ferroelectric microwave resonator

A novel electric and magnetic field tunable microwave resonator with a yttrium iron garnet and barium strontium titanate layered structure is investigated. The measured characteristics at 3.6 GHz, corresponding to the proximity of magnetic and dielectric resonance modes, show a broadband electrical tunability. A tuning range of 1.5% of the central resonance frequency is obtained for nominal electric fields.     

有关电磁噪声复合吸收体技术的介绍（二）

电磁噪声吸收的机理 复合吸收体中电磁噪声被吸收的现象可以在近场和远场应用中被分别解释。在近场应用中,吸收体的磁损耗在吸收高频噪声的过程中发挥着重要的作用。复合吸收体是磁性材料,其特征磁导率在1O到200之间。在低频情况下,这些吸收体具有稳定的磁导率特征。但在更高的频率上,它们显示出二阶磁导率效应。而且,在场强度很高的情况下,