Frequency dependence of microwave complex permeability under magnetic bias (original) (raw)
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Journal of Magnetism and Magnetic Materials, 2019
A new method of studying microwave magnetic properties of metal particles and films is developed. The method is based on measurements with swept frequency under magnetic bias in a coaxial line. Application of the technique is illustrated by the data obtained for two types of samples, washershaped rolls of thin ferromagnetic films and composites filled with flake Sendust particles. The treatment of the measured data is performed with an account for sample demagnetization and anisotropy. The values of the anisotropy field and the saturation magnetization of thin iron films are calculated considering demagnetization of the sample. Because of the anisotropy of the composite samples, permeability depends slightly on the length of samples, and the saturation magnetization and the anisotropy field cannot be determined.
Journal of Magnetism and Magnetic Materials, 2012
Microwave magnetic performance of thin ferromagnetic films is of interest in view of many technical problems. For measuring the microwave permeability, a shorted stripline technique is in common use. Recently, a coaxial technique has been developed for permeability measurements of films deposited onto a flexible substrate. The coaxial technique is reported to be advantageous over the conventional stripline method in wideband operating range and accuracy. In this paper, measurement results are presented which are obtained with these two techniques for Fe-N films. It is found that the magnetoelastic effect contributes greatly to the measured microwave permeability of the films. With the coaxial measurements under an external magnetic bias, this effect may be accounted for to estimate the permeability of a plane film sample. Additional information on the properties of the film can also be extracted from these data, such as estimations of average magnetic anisotropy field and of the magnetostriction constant of the film.
Progress In Electromagnetics Research C, 2009
The strip-line frequency-domain technique for permeability measurement is compared to the field domain technique. The combined setup for microwave measurement of thin film permeability with both techniques is proposed. The field-domain technique is less affected by inhomogeneity of measurement strip cell and has significantly higher signal-to-noise ratio, but the obtained parameters are affected by film thickness and may differ from that of the frequency-domain technique. Analysis of the field-domain data obtained at a set of frequencies makes it possible to determine the saturation magnetisation, the anisotropy field and the damping factor without the knowledge of the amount of substance under study. In case of a simple permeability spectrum the data on metal thickness make it possible to estimate the effective skin-depth as well. The technique is tested by simulation and is applied to determine permeability of Fe-based films vacuum-sputtered on glassceramic and polymer substrates.
2013
In this paper, the main microwave applications of magnetized materials are briefly recalled. The theories developed to predict their dynamic behavior are presented. Then the measurement methods that enable us to compare the theoretical results with experimental data are described. Propects about the needs in new microwave magnetic structures for future applications are finally discussed. We focus these prospects on millimeter self-biased circulators using hexaferrites set in a remanent state. These considerations highlight the need for thorough investigations targeted to the design of magnetized material-based microwave devices to take into account, at the same time, the dc field non-uniformity, the unsaturated state of certain regions of the magnetized substrate and realistic values for the permeability tensor components.
Microwave polarizability of ferrite particles with non-uniform magnetization
Journal of Magnetism and Magnetic Materials, 1999
The microwave permeability of composites made of ferrite particles in a non-magnetic matrix is a!ected by particle shape and size. To account for the second e!ect, we have developed a micromagnetic model for calculating the microwave polarizability of a particle with non-uniform magnetization. This model is described in detail: a generalized demagnetizing operator associated with the equilibrium magnetic con"guration inside the particle is introduced; the polarizability is de"ned as the perturbation of this con"guration by the external magnetic excitation; the permeability of a macroscopic sample is calculated using a space averaging procedure. The numerical methods are introduced and results for two systems are discussed: domain modes in thin "lms and ferrite composites with planar anisotropy.
Microwave and static magnetic properties of multi-layered iron-based films
Journal of Magnetism and Magnetic Materials, 2009
Thin ferromagnetic films with in-plane magnetic anisotropy are promising materials for obtaining high microwave permeability. To produce a bulk massive sample from thin films, multi-layer films made of a number of many thin films may be used. The paper reports on an experimental study of microwave and static magnetic properties of multi-layer iron-based films and composite samples made of these. The multi-layer films under study are deposited onto a mylar substrate by a magnetron-sputtering process performed in Ar atmosphere with controlled N 2 admixture. The sputtered iron layers are alternated with SiO 2 layers. The measured static and microwave magnetic properties of the bulk sample are found to differ from the properties of constituent films. This is an evidence for strong interactions between the magnetic layers in the sample, which interact at distances exceeding greatly the distance between adjacent magnetic layers. A theoretic model is developed to account for magneto-dipole interactions between iron films in a multi-layer system. The model explains the anomalously high demagnetization field of the sample observed in the measurements.
Journal of magnetism …, 2005
Dynamic permeability measurements of soft magnetic films are performed and their corresponding domain configurations are observed with a Kerr effect microscope. Measurable discrepancies can be observed between the effective permeabilities of layers of different macroscopic sizes and in layered structures. These effects can be associated with the presence of a domain configuration at the edges of the sample. A phenomenological method is proposed to describe these discrepancies. It is supposed that a region at the edge of the sample exhibits a perturbed microwave permeability with lower frequency signals. These outcomes have consequences on the conception of devices using high permeability layers.
Experimental study of microwave permeability of thin Fe films
Journal of Magnetism and Magnetic Materials, 2003
The paper deals with the microwave permeability of thin Fe films deposited on a mylar substrate under different technological conditions. The permeability is measured in the 100MHz–10GHz range using coaxial techniques and below 100MHz using the single coil and single wire techniques. Magnetically uniform films were deposited by ion beam sputtering and revealed the most suitable magnetic properties. Magnetron deposited
Broadband Microwave Measurements of Relative Permittivity and Permeability of Materials
A short review of modern techniques for broadband microwave measuring complex permittivity and permeability of materials at broadband microwave frequencies has been presented. Classification of type of the measurement methods to extract the complex permittivity and permeability of bulk materials has been done in this paper. Mathematical models of all the above-mentioned measurement types of methods are reviewed. Advantages and disadvantages of existing measurement devices/systems are described according to the classification made. A new design of test devices for the measurement system operating in broadband microwave frequency range has been proposed. Measurement system on the basis of the proposed device can be used for a measuring the ordinary bulk materials, ferrites (including fully magnetized) and magnetic materials but much cheaper then one to be made. The system is much cheaper than a free space measurement system. The approach to define the permeability tensor of magnetic m...