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All Journal Makara Journal of Science
Dede Djuhana
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Journal : Makara Journal of Science

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Micromagnetic Study on the Magnetization Reversal of Barium Hexaferrite (BaFe12O19) Thin Film Djuhana, Dede; Oktri, Dita; Kurniawan, Candra
Makara Journal of Science Vol. 22, No. 4
Publisher : UI Scholars Hub

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This study investigates a magnetization reversal mechanism based on the hysteresis curve of Barium Hexaferrite (BFO) thin film by micromagnetic simulation through parallel and perpendicular magnetization directions along the axes. The hexagonal shape of the BFO film was modeled with thicknesses of 5, 10, and 15 nm and a diameter size ranging from 50 to 100 nm. It was found that the coercivity field HC and the saturation field HS of the BFO film decreased as thediameter size increased and thickness decreased. It was observed that the nucleation field HN increased as the diametersize increased. An analysis of energies showed that the demagnetization energy was dominantly influenced by the diameter and thickness in comparison to the anisotropic energy. From the hysteresis curve, the switching time was also investigated. Interestingly, the switching time was faster for the thinner BFOs with a diameter under 70 nm. For particles larger than 70 nm in diameter, the switching time showed fluctuation irrespective of the BFO thickness. Based on these results, a diameter size of 70 nm is proposed as the critical size for producing the equal time for switching domain polarity.
Micromagnetic Simulation of the Depinning Field Domain Wall on Symmetric Double Notch Ferromagnetic Wires Djuhana, Dede; Supriyanto, Erwin; Kim, Dong Hyun
Makara Journal of Science Vol. 18, No. 2
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In this paper, we investigate the depinning field domain wall on symmetric double notch ferromagnetic wires by means of micromagnetic simulation for Permalloy (Py), Cobalt (Co), and Nickel (Ni) materials. The depinning field domain wall increases as the size of the notch decreases. At a lower depinning field, the domain wall inner structure exhibited a transverse wall (TW), while at a higher depinning field, there was a transformation of the domain wall inner structure from transverse wall to antivortex wall (AVW). We also observed that the magnetization energy increased as the size of the notch decreased. This means that more energy was needed to release the domain wall from a smaller notch. Micromagnetic simulation showed that the depinning field domain wall depends on the size of the notch and on the ferromagnetic anisotropy.
Effect of Niobium Addition on Corrosion Behavior, Mechanical Properties, and Microstructures of U6Zr Alloys in an Aerated Environment Masrukan, Masrukan; Handoko, Djati; Djuhana, Dede; Sigit, Rohmad; Al Hasa, M. Husna; Adi, Wisnu Ari; Mardiah, Siti
Makara Journal of Science Vol. 29, No. 4
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The effect of Nb addition on the corrosion behavior of U–6Zr alloys within an aerated, demineralized water (DW) environment (pH 5.61) and its correlation of this addition with the mechanical and microstructural properties of the alloys were investigated. The U–6Zr–xNb alloys (x = 1, 4, and 7 wt.%) were synthesized by arc-melting U, Zr, and Nb. Additionally, the samples were mounted and polished, after which they were subjected to electrochemical corrosion analysis using a potentiostat. This evaluation was conducted in a DW medium (pH 5.6), representing an aerated atmosphere, at room temperature (27°C) and a potentiodynamic scan rate of 1 mV/cm2. The results demonstrate that Nb addition to the U–6Zr alloy, which yielded a U–6Zr–xNb (x = 1.4 and 7 wt.%) alloy, influenced the corrosion behavior in media, exhibiting a slightly acidic pH (5.61). Nb additions of up to 4 wt.% caused a continuous increase in the open-circuit potential, corrosion-current density, and corrosion rate (CR); however, these values decreased with the continuous increase in Nb concentrations to 7 wt.%. Furthermore, microstructural analysis via scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed that the corrosion products across almost all U–6Zr–xNb test samples (x = 0, 1, 4, and 7 wt.%) were primarily stable uranium dioxide, which formed a protective layer, followed by oxynitride and zirconium(IV) oxide.Overall, the findings indicated that the varying Nb contents (1, 4, and 7 wt.%) dictated the CR, mechanical properties, and microstructure of the alloys. Ultimately, this study demonstrates the synthesis of U–6Zr–xNb alloys (x = 0, 1, 4, and 7 wt.%) with enhanced performance characteristics.
Co-Authors Candra Kurniawan Candra Kurniawan Dita Oktri Dong Hyun Kim Erwin Supriyanto Handoko, Djati Kim, Dong Hyun M. Husna Al Hasa Masrukan Masrukan Oktri, Dita Sigit, Rohmad Siti Mardiah, Siti Supriyanto, Erwin Wisnu Ari Adi