Frequency Dependence Of Permeability Research Articles

Frequency dependence of microwave complex permeability under magnetic bias

Measurement of the frequency dependence of the permeability under magnetic bias is proposed as a new method for studying the microwave magnetic properties of magnetic materials. The samples under study are either rolls of thin ferromagnetic films or the composites filled with sendust particles. It is shown that the permeability measured under external magnetic bias depends on sample thickness. The correct interpretation of the measured data is possible only when sample demagnetization is accounted for. The values of the anisotropy field and the saturation magnetization of thin nitrogen doped iron films and flake-shaped sendust particles are calculated considering demagnetization of the washer-shaped sample.

Effect of Annealing Temperature on the Complex Permeability of (Fe0.95Co0.05)73.5Cu1Nb3Si13.5B9 Nanocrystalline Amorphous Ribbon

FINEMET-like amorphous ribbon of composition (Fe0.95Co0.05)73.5Cu1N b3Si13.5B9 was prepared by rapid quenching method in an Argon (Ar) atmosphere. The alloy has been annealed in a controlled way in the temperature range of 550 to 750°C for 30 minutes. Nanocrystalline state was evaluated by X-ray diffraction (XRD). In the range of annealing temperature (Ta), the grain size has been found in the range of 9-26 nm. Frequency dependence of permeability of amorphous and nanocrystalline toroid shaped samples have been measured. The low frequency initial permeability for the optimum annealed samples has been found to 5.8 × 103 and the highest value of quality factor is found for the sample annealed at 550°C; which also indicates the best heat treatment temperature.

Частотная зависимость магнитной проницаемости помогает различать марки стали

Частотная зависимость магнитной проницаемости помогает различать марки стали

Effect of magnesium on relaxation frequency of Ni–Zn nanoferrites

[Formula: see text] (x = 0, 0.4, 0.8, 0.10, 0.12 and 0.16) samples have been synthesized by sol–gel method using polyvinyl alcohol (PVA) as chelating agent. The synthesized samples were sintered at 1000[Formula: see text]C for 1 h. The X-ray diffraction (XRD) confirms single phase spinel structure and scanning electron microscope (SEM) confirms the uniform grain with increasing grain growth with increase concentration of magnesium (Mg) (x). A slight increase in saturation magnetization (VSM) has been observed for low concentrations of magnesium which disappear for higher concentrations of magnesium [Formula: see text] in these materials. Decrease in room temperature DC resistivity with magnesium concentration has been attributed to grain growth. The permeability measured for the ferrites exhibits high permeability for increase in the magnesium content. The permeability behavior is understood on the basis of domain wall contribution and grain growth. Frequency dependence of permeability as measured suggests that the suitability of all the samples for high frequency core applications as the operating frequency lies beyond 110 MHz.

Effects of heating processing on microstructure and magnetic properties of Mn-Zn ferrites prepared via chemical co-precipitation

The fine powders of Mn-Zn ferrites with uniform size were prepared via chemical co-precipitation method. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), frequency dependence of permeability and metallographical microscope were used to investigate the crystal structure, surface topography and magnetic properties of the powders and the sintering samples. The experimental results demonstrate that the precursor powders have formed a pure phase cubic spinel Mn x Zn1−x Fe2O4 while in the reactor and show definite magnetism, which can solve the difficult issue in washing process effectively. When calcined beneath 450 °C, the powders have intact crystal form and the crystallite size is less than 20 nm. Comparison tests of sintering temperatures show that 1 300 °C is the ideal sintering temperature for Mn-Zn ferrites prepared by using the chemical co-precipitation.

AC magnetic properties of nanogranular FeCo-AlN films

Nanogranular magnetic FeCo–AlN films were fabricated by plasma jet technique. Magnetic anisotropy in the films was induced by applied external magnetic field during the deposition. X-ray diffraction and chemical analysis revealed that the films consist of crystalline FeCo grains with the size of about 10 nm and amorphous AlN matrix. Hysteresis loops were measured using an AC hysteresis loop tracer at 101 Hz. The frequency dependence of permeability was investigated in the range of 0.1–2 GHz by a strip line permeameter. The highest characteristic frequency at which the natural ferromagnetic resonance occurs is about 1.7 GHz. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Fe–N films: Morphology, static and dynamic magnetic properties

The study is conducted of thin Fe–N films produced by magnetron sputtering on mylar substrate. The correlations between morphology, structure, and magnetic static and dynamic properties of the films are found. The films under study have a columnar morphology. Both the average granule size and the length-to-width ratio of the granules increase with the film thickness that causes an increase of the effective anisotropy field. A small variation of nitrogen fraction in Ar+N2 gas mixture in the sputtering chamber allows the location of magnetic loss peak to be controlled within the frequency range of 1–5GHz. Therefore, the frequency dependence of permeability is determined not only by the crystalline structure and composition of the film but also by its morphology, thickness, and effective magnetic anisotropy. In particular, with the fixed concentration of nitrogen in the film, the frequency dependence of microwave permeability is determined greatly by the distribution of nitrogen atoms over different vacancies in the film structure.

가스 분무법으로 제조된 NixFe100-x(x=40~50) 퍼멀로이 분말 및 압분 코아의 자기적 특성

가슨 분무법으로 제조한 High-Flux형 <TEX>$Ni_{x}Fe_{100-x}$</TEX>(x=40~50, wt.%) 퍼멀로이 분말 및 압분 코아의 자기적 특성을 조사하였다. 포화자화는 45%Ni조성에서 최대 값을 보이며 이보다 보 함량이 낮아지면 인바 효과의 작용에 의해 급격하게 감소하였다. 압분 코아의 투자율은 Ni 농도가 낮아지면 현저히 증가하는 바 이는 자기변형의 감소에 기인하는 것으로 사료되었으며, 자심손실은 Ni=45%에서 가장 낮은 값을 나타내었다. Ni농도가 50%에서 45%로 낮아짐에 따라 자심손실이 감소하는 주원인은 전기 비저항의 증대에 따른 와전류 손실의 감소에 있는 것으로 생각되었다. Ni=45% 분말 합금으로 만든 압분 코아는 Ni=50%의 경우보다 더 우수한 투자율의 주파수 의존성, 큰 Q 값, 그리고 더 나은 직류 바이어스 특성을 나타내어 상용 High-Flux 코아(50%Ni-50%Fe)에 비해 더 좋은 압분 자심 재료가 될 수 있음을 확인하였다. We investigated the magnetic properties of High Flux-type <TEX>$Ni_{x}Fe_{100-x}$</TEX>(x=40∼50, wt.％) permalloy powders and dust cores. The powder was prepared by conventional gas atomization in mass production scale. At the composition of <TEX>$Ni_{x}Fe_{55}$</TEX>, saturation magnetization was maximum. In case of lower Ni content than X=45, the <TEX>$M_{s}$</TEX>, decreased largely with the decrease in Ni content, which is due to the invar effect. The permeability of compressed powder cores increased with the decrease in Ni content, which was considered to be due to the decrease in the magnetostriction. In addition, the dust core with Ni=45％ showed the lowest core loss because of the increase in electrical resistivity leading to the low eddy current loss. From the better frequency dependence of permeability, larger Q value and superior DC bias characteristics of Ni=45％ than those of Ni=50％ core, it was confirmed that the 45％Ni-55％Fe powder alloy was better material for the dust core than commercial High Flux core materials.

The evolution of soft magnetic properties and the related density change during amorphous–nanocrystalline transformation

The frequency dependence of permeability and power loss are investigated in FINEMET samples after isothermal heat treatments, leading to structural relaxation and/or nanocrystallization. The rapid decrease in power loss and increase in permeability at low frequencies are connected mainly with the structural relaxation and the first period of nanocrystallization. The time scale for the evolution of soft magnetic properties at high frequencies is similar to that for the density change.

High frequency properties of glass-coated microwire

Static and high-frequency 1–30 MHz properties of the (Co100−xMnx)75B15Si10 microwires cast using the modified Taylor’s technique are reported. The hysteresis loop and the frequency dependence of permeability indicate that the longitudinal magnetization process occurs by coherent rotation of the moments. The values of static permeability are in good agreement with those predicted by the theory of ferromagnetic resonance where damping is taken into account. We observed a close correlation between the static permeability and the high-frequency limit (the frequency up to which the real part of permeability is still constant). For glass-coated CoMn microwires, this limit is considerably higher than that given by the Snoek equation.

The frequency dependence of permeability in Co 66.5Fe 3.5Si 12B 18 metallic glasses

The influence of the drive frequency on the reversible permeability in toroidal cores consisting of amorphous CoFeSiB ribbons in the as-quenched state and subjected to different annealing treatments has been studied. The frequency dependence of the real and imaginary parts of the permeability, as well as the core losses, are also analysed at frequencies up to 40 MHz and for low drive fields.

Magnetic domain structures and dynamics of CoTaZr/Cr multilayered films

The permeability, domain structure, and dynamic magnetization change of CoTaZr/Cr multilayered stripes are studied. The frequency dependence of permeability is improved by lamination with Cr layers, which eliminates the closure domain structure. An edge curling wall (ECW) is observed near the edge of the multilayered stripes. The width of the ECW agrees well with calculations and is independent of stripe width. The magnetization in the ECW is difficult to rotate by the external magnetic field; therefore, the permeability of a narrow stripe is less than that of wider stripes.

Frequency Dependence of Permeability in Fe-Zr-N Film

The effects of the thickness, uniaxial anisotropy field, electrical resistivity and addition of other elements on the frequency dependence of permeability in Fe-Zr-N films were investigated. Film thicknesses were varied up to 8 ?m. The purpose of this study was to identify the main origin of the high-frequency loss in thick films in order to allow them to be applied in magnetic heads. The results showed that the main origin of the loss in high-anisotropy film was eddy currents. Although an anisotropy dispersion existed, the permeability at magnetic head-driving frequencies below 30 MHz can be explained using the classical equation for eddy current losses with an effective uniaxial anisotropy field. On the other hand, the permeability of low-anisotropy film disagreed with the results obtained from the classical equation. The effect of anisotropy dispersion must be considered in order to explain the permeability of these low-anisotropy films.

巻線型薄膜インダクタにおける高Ｑ化のためのストリップ状磁心の検討

In this paper, a new type of strip-like magnetic core is proposed. The structure of this core is prepared by separating the nearest-neighbor strip, Which is made of SiO2, by a gap (d), and then sputtering a magnetic film under an external field applied in a perpendicular to the exciting direction. The width of the strip lines(Ws)varied from 10∼1000μm. The arrangement of these high-density strip lines is confirmed by the domain structure and the frequency dependence of permeability. When the gap is greater than the thickness of the magnetic film, the magnetic domains are independent of each other, and the initial permeability is the same as that of the strip line film which is separated by space. When the strip width is decreased, the domain width decreases and the number of domains increases. The strip-like magnetic core is used in a thin film inductor. The inductance at 20 MHz and the maximum value of quality factor (Qmax) in the experimental inductor show maxima at about Ws=300∼500μm. This magnetic core is useful for increasing the inductance and quality factor of thin-film inductors.

Fe-Zr-N膜の透磁率の周波数特性

The effects of thickness, uniaxial anisotropy field, electrical resistivity, and element addition on frequency dependence of permeability in Fe-Zr-N films were investigated. Film thickness was up to 8μm. The purpose of our study was to clarify the main origin of high frequency loss in those thick films in order to apply them to magnetic heads. The results showed that the main origin of loss was eddy current for high anisotropy film. Although anisotropy dispersion existed, permeability for magnetic head drive frequency of lower than 30 MHz is explained by using the classical equation of eddy current loss with the effective uniaxial anisotropy field. On the other hand, the permeability for low anisotropy film disagrees with the result obtained by the classical equation. The effect of the anisotropy dispersion should be considered to explain the permeability of those low anisotropy films.

Permeability and Anisotropy Dispersion of Amorphous Soft Magnetic Films

The frequency dependence of permeability has been calculated for soft magnetic thin films which have a uniaxial anisotropy with both amplitude and angular dispersion. These calculations have been performed for amorphous Co-Nb films, whose anisotropy dispersion has been determined by low-frequency FMR measurements. Comparison of the measured permeability with calculations suggests that the effective uniaxial anisotropy is dispersed more widely and with a smaller amplitude than is indicated by FMR measurements. The magnetization ripple is inferred to be one of the causes of the low value for the effective field.

軟磁性アモルファススパッタ膜の透磁率と異方性分散

Frequency dependence of permeability has been calculated for soft magnetic thin films which have amplitude and angular dispersion of the uniaxial anisotropy. The calculation has been adopted for amorphous Co-Nb films whose anisotropy dispersion has been determined by low frequency FMR measurements. Comparison of the measured permeability with the calculation suggests that the effective uniaxial anisotropy is dispersed more widely with low values than that obtained by the FMR method. The magnetization ripple is deduced to be one of the origins of the low effective field.