FRACTAL ANALYSIS OF THE MAZE-LIKE DOMAIN STRUCTURE OF FERRITE-GARNET FILMS IN THE PROCESS OF MAGNETIZATION

В данной работе с использованием комплекса экспериментальных методик и специализированного программного обеспечения исследуются магнитные висмутсодержащие феррит-гранатовые пленки, выращенные на подложках из гадолиний-галлиевого граната. Методом оптической магнитометрии получены предельные петли магнитного гистерезиса для дефектных и бездефектных участков висмутсодержащих феррит-гранатовых пленок. Установлено, что вдали от дефектов петля демонстрирует бескоэрцитивное поведение в пределах погрешности. Для случая перемагничивания вблизи дефекта появляется коэрцитивное состояние с H~1 Э. Для разных участков предельной петли магнитного гистерезиса определена фрактальная размерность. Полученные значения лежат в диапазоне D=1,35÷1,46 для произвольного участка пленки и D=1,37÷1,54 для участка с дефектами. Определены типичные морфологические характеристики поверхности висмутсодержащей ферритгранатовой пленки. Полученные результаты позволяют для эпитаксиальных висмутсодержащих магнитных пленок феррит-граната прогнозировать взаимосвязь между значением намагниченности и значением фрактальной размерности. In this work, using a set of experimental techniques and specialized software, magnetic bismuth-containing ferrite-garnet films grown on gadolinium-gallium garnet substrates are investigated. The limiting magnetic hysteresis loops are obtained by the method of optical magnetometry for defective and defect-free areas of bismuth-containing ferrite-garnet films. It was found that, far from defects, the loop exhibits a non-coercive behavior within the error limits. For the case of magnetization reversal, a coercive state with H ~1Oe appears near the defect. For different sections of the limiting magnetic hysteresis loop, the fractal dimension is determined. The obtained values are in the range of D=1,35÷1,46 for an arbitrary section of the film and D=1,37÷1,54 for a section with defects. Typical morphological characteristics of the surface of a bismuth-containing ferrite-garnet film have been determined. The results obtained make it possible to predict the relationship between the value of magnetization and the value of fractal dimension for epitaxial bismuth-containing magnetic films of iron garnet.

Reducing the Internal Stress of Fe-Ni Magnetic Film Using the Electrochemical Method

Soft magnetic materials are important functional materials in the electrical engineering, radio, and high-tech fields, but thin and brittle flakes present challenges to the manufacturing industry. In this study, the effect and mechanism of saccharin sodium in reducing the internal stress of Fe-Ni magnetic films were analyzed. The effects of the pH value, temperature, and the concentration of saccharin sodium on the deposition process of Fe-Ni alloys were investigated. The polarization curve of the Fe-Ni alloy deposition process was measured by using a multifunctional electrochemical workstation, and the morphology and crystal structure were measured by a scanning electron microscope (SEM) and X-ray diffraction (XRD). The results show that saccharin sodium significantly reduced the stress of the iron-nickel magnetic film; the mechanism through which the internal stress was reduced is analyzed in this paper. Briefly, the Fe2+ and the amino group of saccharin sodium synthesized a metal complex with positive charge on the surface of the electrode, which prevented the hydrogen ions from approaching the cathode and increased the discharge activation energy of the hydrogen ion, which reduced the hydrogen evolution and improved the internal stress of the coating. This research will help to solve the challenges of producing magnetic film, and promotes the application of new stress-reducing agents.

Coercivity Mechanism and Magnetization Reversal in Anisotropic Ce-(Y)-Pr-Fe-B Films

In this study, the magnetic properties, coercivity mechanism, and magnetization reversal process were investigated for Ce-(Y)-Pr-Fe-B films. After the addition of Y and subsequent heating treatment, the formations of REO (RE ≡ Ce and Pr) and REFe2 (RE ≡ rare earths) phases are inhibited, and the microstructure of Ce-Y-Pr-Fe-B film is optimized. Meanwhile, the coercivity and the squareness of the hysteresis loop are significantly improved. The coercivity mechanism of Ce-Y-Pr-Fe-B film is determined to be a mixture of nucleation and pinning mechanisms, but dominated by the nucleation mechanism. The demagnetization results show that the nucleation of reversal magnetic domains leads to irreversible reversal. Our results are helpful to understand the coercivity mechanism and magnetization reversal of permanent magnetic films with multi-main phases.