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Title: 橢圓奈米磁石之微波輔助磁化翻轉研究
Study of microwave-assisted magnetization switching of elliptical nanomagnets
Authors: Yong-Sheng Wang
Contributors: NTOU:Institute of Optoelectronic Sciences
Keywords: 微波磁化
Date: 2009
Issue Date: 2011-07-04
Abstract: 本論文運用微磁學探討橢圓鐵磁體磁化於偏壓磁場及微波輔助下之翻轉行為;研究結果顯示,其磁化翻轉行為深受偏壓磁場、微波振幅與頻率的影響。當微波頻率接近於磁化共振頻率時,能量可有效地注入而使磁化進動振幅增大,然而當微波頻率偏離磁化共振頻率時,微波輔助效益則將減弱甚至消失。與無微波輔助情況作比較,藉微波輔助於最佳化微波頻率時,可顯著地降低翻轉磁化所需的偏壓場強度。為了最大化微波輔助效益,最佳化微波頻率須隨偏壓場指向、微波極化型式及振幅而調變,並與巨自旋模型所預測的鐵磁共振頻率明顯不同,這緣由為橢圓鐵磁體因非橢圓形狀之故,其磁化翻轉實際上是經由非均勻磁化轉動模式發生。
In this thesis, we utilize the micromagnetics to explore the switching behavior of magnetization of elliptical ferromagnets under the action of biased magnetic fields with the assistance of microwaves. The studies show that the magnetization switching critically depends on the orientation of bias fields, and the polarization mode and amplitude of microwaves. As the frequency of microwaves is close to that of magnetic resonance of ferro- magnet, the energy can be effectively pumped into the system, and the amplitude of magnetization precession is enhanced; however, as the two frequencies differ, the benefit of the microwave is weak, even disappears. Compared with the case of null microwave assistance, the bias field strength required to switch the magnetization by the present method can be lowered significantly at the optimal frequency of microwaves. In order to maximize the benefit of microwave assistance, the optimal frequency of microwaves depends on the orientation of bias fields, and the polarization mode and amplitude of microwaves, and distinctly differs from the fre- quency given by the ferromagnetic resonance according to the macrospin model. The reason for this deviation is that the magnetization switching of elliptical ferromagnets indeed occurs via the mode with non-uniform rotation of magnetization, resulting from the non-ellipsoidal shape. 5
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0M95880028
Appears in Collections:[光電科學研究所] 博碩士論文

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