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Magnetic Permeability Distribution in Amorphous Magnetic Microwiresтезисы доклада
- Авторы: Perov N., Alekhina Y., Baraban I., Khairullin M., Kolesnikova V., Komlev A., Makarova L., Rodionova V.
- Сборник: INTERMAG 2020 Digests
- Серия: INTERMAG
- Том: 1
- Тезисы
- Год издания: 2020
- Издательство: Institute of Electrical and Electronics Engineers
- Местоположение издательства: Piscataway, NJ, United States
- Первая страница: 502
- Последняя страница: 502
- Аннотация: Amorphous magnetic materials have the pronounced soft magnetic properties, high resistivity, giant magneto-impedance effect — the dependences of the complex resistance on the magnetic field — and bistability of magnetization state, that make it possible to create electrical machines with enhanced efficiency [1], highly sensitive magnetic field sensors, in particular, for geomagnetic applications or biomolecules sensing [2-5], and binary elements for storage devices [6]. Moreover, the use of amorphous and nanocrystalline materials for hyperthermia was also described in literature [7]. The peculiarities of their behavior under magnetic field make it possible to shed light on the formation mechanisms of various properties of magnetic materials, which are one of the key issues in the field of physics of magnetic phenomena and justifies the importance of amorphous materials investigations from the fundamental science point of view. Complex micromagnetic structure of amorphous microwires and the dependence of magnetic permeability on magnetic field account for the nontrivial permeability distribution over the cross-section of the sample. Nonuniform permeability distribution over the sample volume contributes to the magnetic response of the system, what makes its investigations crucial for further understanding of magnetic properties formation on the microlevel. For the reconstruction of the permeability distribution numerical calculations were combined with experimental investigations. Data on impedance characteristics of the sample allows one to restore the value of magnetic permeability. Frequency dependence of the skin-depth makes it possible to involve different fractions of the wire into the process of remagnetization by current. Thus, frequency dependences of impedance allow one to obtain integral permeability values of wire shells having different thickness. Assuming the additive character of magnetic permeability, its distribution over the cross-section of the wire can be reconstructed layer by layer. Experimental investigations of the impedance of amorphous microwires were conducted using vector network analyzer Agilent FieldFox N9923A in the frequency range from 2MHz to 6GHz. External magnetic field was created by coil with the thickness of 4 cm and diameter 15 cm having 1500 turns of the wire. Field magnitude was varied in the range ±100 Oe. The sample of the amorphous microwire with the length of 2cm was soldered to the substrate and then fixed in a measuring cell that can be included into the coaxial transmission line. For the investigations 4 samples of amorphous microwires of Fe6.1Co57Ni10B15.9Si11 composition having metal core diameters 7.6, 9.4, 14.4, 20.4 μm were chosen. Static magnetic properties of the samples were investigated using vibrating sample magnetometer VSM LakeShore 7400 Series at room temperature and were used as reference parameters for further calculations. Calculations for reconstruction of the permeability distribution were conducted using Matlab software on the basis of inline functions. As a first step to permeability restoration calculations of impedance and GMI effect were made based on classical approach of constant permeability of cylindrical wire: Z=R*kR*- J0(kR)/2*J1(kR), where k=(1+i)/δ, δ=c/sqrt(2πλμω). Values of calculation parameters were chosen according to the experimental data. Comparison of the values of GMI obtained in experiment and those obtained as a result of calculations allows one to see the divergence between real experiment and classical approach. The magnitude of this divergence depends on the experimental circumstances – metal core diameter, frequency and so on. Classical approximation considers permeability as a constant parameter, and its dependence on the radial coordinate is not taken into account. In real microwire, permeability is distributed extremely heterogeneous over the cross-section of the microwire. With increasing frequency of the flowing current the fraction of the sample volume involved in the remagnetization process decreases due to the skin effect. As the permeability reduces when approaching the surface of the wire in reference to the permeability in zero field used for calculations, measured values of GMI also strongly decrease. Thus, the difference between the calculations based on the classical approximation and experimental data confirms the initial assumptions of this research and the importance of its implementation. Experimental results for frequency dependences of impedance and GMI effect were processed according to the described methodology. For each frequency and, thus, for each skin depth the value of effective magnetic permeability was obtained. Assuming the additive character of the permeability function, the contribution of each layer into magnetic response was restored. The dependence of the permeability on the radial coordinate was then obtained. The authors acknowledge support from M.V. Lomonosov Moscow State University Program of Development and Russian Fund for Basic Research No 18-02-00137. YA and NP were supported with Russian Fund for Basic Research No 19-32-90089.
- Добавил в систему: Комлев Алексей Степанович