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Abstrak :
[ABSTRAK
Pada laporan akhir tesis ini telah dikembangkan suatu sistem untuk magnetisasi bahan magnet menjadi magnet permanen dan demagnetisasi dengan mengurangi kuat medan magnet suatu magnet permanen. Sistem ini digunakan untuk magnetisasi bahan magnet seperti Ferit, PrFeB, NdFeB dan jenis bahan magnet yang lain. Bahan magnet dapat dimagnetisasi menjadi magnet permanen dengan menerapkan medan magnet sampai diatas titik saturasi magnet dari bahan magnet pada waktu singkat atau dikenal dengan impulse magnetizer. Penerapan medan magnet menghasilkan momen magnetik dan memaksa domain-domain magnetik secara bertahap mengikuti arah medan magnet yang diterapkan. Jika medan magnet eksternal lebih kuat dari medan magnet saturasi magnetik dari bahan magnet maka domain-domain magnetik akan diorientasikan dengan arah yang baru. Sistem ini menggunakan kapasitor untuk menyimpan muatan listrik dan kemudian diterapkan pada lilitan kawat berbentuk solenoid multi lapis. Pada tesis ini telah berhasil melakukan magnetisasi dan demagnetisasi bahan magnet Ferit, PrFeB dan NdFeB dengan ukuran bahan maksimal 26mm.

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ABSTRACT
On this nal thesis report has been developed a system for the magnetization of the magnetic material become permanent magnets and demagnetization by reducing the magnetic eld strength of a permanent magnet. This system is used for magnetize the magnetic material such as Ferrite, PrFeB, NdFeB magnets and other types of magnetic materials. Magnetic material can be magnetized into a permanent magnet by applying a magnetic eld above the saturation point of the magnetic material in a short time, known as impulse magnetizer. Application of a magnetic eld generates a magnetic moment and domain-domain magnetic force gradually follow the direction of the applied magnetic eld. If the external magnetic eld is stronger than the magnetic eld of a magnetic saturation of the magnetic material, the magnetic domains will be oriented to the new direction. This system uses a capacitor to store electrical charge and then applied to the multi-layer solenoid or coil by discharging process. On this thesis has been successfully doing magnetization and demagnetization magnetic materials such as Ferrite, NdFeB, PrFeB with a maximum material size of 26mm.;On this nal thesis report has been developed a system for the magnetization of the magnetic material become permanent magnets and demagnetization by reducing the magnetic eld strength of a permanent magnet. This system is used for magnetize the magnetic material such as Ferrite, PrFeB, NdFeB magnets and other types of magnetic materials. Magnetic material can be magnetized into a permanent magnet by applying a magnetic eld above the saturation point of the magnetic material in a short time, known as impulse magnetizer. Application of a magnetic eld generates a magnetic moment and domain-domain magnetic force gradually follow the direction of the applied magnetic eld. If the external magnetic eld is stronger than the magnetic eld of a magnetic saturation of the magnetic material, the magnetic domains will be oriented to the new direction. This system uses a capacitor to store electrical charge and then applied to the multi-layer solenoid or coil by discharging process. On this thesis has been successfully doing magnetization and demagnetization magnetic materials such as Ferrite, NdFeB, PrFeB with a maximum material size of 26mm., On this nal thesis report has been developed a system for the magnetization of the magnetic material become permanent magnets and demagnetization by reducing the magnetic eld strength of a permanent magnet. This system is used for magnetize the magnetic material such as Ferrite, PrFeB, NdFeB magnets and other types of magnetic materials. Magnetic material can be magnetized into a permanent magnet by applying a magnetic eld above the saturation point of the magnetic material in a short time, known as impulse magnetizer. Application of a magnetic eld generates a magnetic moment and domain-domain magnetic force gradually follow the direction of the applied magnetic eld. If the external magnetic eld is stronger than the magnetic eld of a magnetic saturation of the magnetic material, the magnetic domains will be oriented to the new direction. This system uses a capacitor to store electrical charge and then applied to the multi-layer solenoid or coil by discharging process. On this thesis has been successfully doing magnetization and demagnetization magnetic materials such as Ferrite, NdFeB, PrFeB with a maximum material size of 26mm.]

Abstrak :
Pada penelitian ini telah dilakukan pengamatan dinamika domain-wall pada material feromagnet berbasis Co CoFe, CoFeB dan Fe FePt, FePd dalam bentuk nanowire. Analisis dilakukan dengan menggunakan simulasi mikromagnetik berdasarkan persamaan Landau-Lifshitz Gilbert LLG yang dimodifikasi menggunakan perangkat lunak mikromagnetik OOMMF Object Oriented Micromagnetic Framework Donahue and Porter, 1999. Ukuran dan geometri dari nanowire mempunyai panjang 2000 nm, dengan variasi lebar 50 nm, 100 nm, 150 nm dengan tebal 2,5 nm dan 5 nm. Faktor damping 0,05 dan ukuran sel 5 x 5 x t nm3 dengan t adalah ketebalan nanowire. Simulasi dinamika domain-wall ini menggunakan pulsa medan magnet aktif dengan durasi 0,5 ns serta variasi pemberain medan magnet luar menyatakan amplitudo pulsa. Hasil simulasi memperlihatkan kecepatan domain-wall meningkat dengan bertambahnya medan magnet luar sampai medan magnet luar maksimum atau yang dikenal dengan medan Walker Breakdown WB . Kemudian, kecepatan domain-wall akan menurun drastis. Menariknya, kondisi sebelum medan WB menunjukan struktur transverse-wall sedangkan struktur vortex/antivortex-wall muncul setalah medan WB. Jika pemberian variasi tebal dan lebar pada geometri nanowire semakin besar maka hasil menunjukkan bahwa medan WB akan semakin menurun. Hasil pengamatan juga melibatkan energi demagnetisasi yang meningkat dengan bertambahnya medan magnet luar sebelum medan WB dan energi exchange yang meningkat ketika struktur vortex/antivortex-wall muncul setelah medan WB.

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In this study we have observed the propagation of domain wall in Co based ferromagnetic materials CoFe, CoFeB and Fe FePt, FePd in the form of nanowire. The analysis was performed using a micromagnetic simulation based on the Landau Lifshitz Gilbert LLG equation modified using the OOMMF Object Oriented Micromagnetic Framework micromagnetic software Donahue and Porter, 1999. The size and geometry of nanowire has a length of 2000 nm, with variations in width 50 nm, 100 nm, 150 nm with 2.5 nm and 5 nm thickness. Damping factor 0.05 and cell size 5 x 5 x t nm3 with t is nanowire thickness. This domain wall dynamics simulation uses active magnetic field pulses with a duration of 0.5 ns and an external magnetic field variation represents pulse amplitudes. The simulation results show that the domain wall velocity increases with the increase of the external magnetic field to the maximum outer magnetic field known as the Walker Breakdown WB field. Then, the domain wall speed will decrease dramatically. Interestingly, the condition before the WB field shows the transverse wall structure whereas the vortex antivortex wall structure appears after the WB field. If the variation of thickness and width in nanowire geometry is greater then the result indicates that the WB field will decrease further. The observations also involve increased demagnetization energy by increasing the external magnetic field before the WB field and increasing energy exchange when the vortex antivortex wall structure appears after the WB field.