有缺陷之準一維系統磁區動力學

Abstract

本文主要是以數值模擬的方法研究缺陷對於準一維磁區動力學之影響。在此 研究中，我們設計了一個帶有四個缺陷之鐵磁奈米條紋，其系統磁化含有兩個磁 區，在兩磁區之間含有一頭對頭的磁區壁，且其磁化在系統兩端為固定，接著注 入沿平面流動之自旋偏極化電流，藉以驅動磁區壁移動；由於缺陷之影響，此系 統之磁化形成了兩個穩定態，應用不同電流密度之自旋偏極化電流，可驅使磁化 在兩穩定態之間轉換。我們發現，在電流關閉時，磁區壁會有反彈的效應，而此 效應只有在電流密度大於jcriticle且電流下降時間小於2 109秒時出現。 由於應用此效應，可以使用同方向之直流電控制磁區壁之位置，進而使元件更加簡化，因此反彈效應在自旋扭矩傳輸相關之元件設計有許多應用潛力。

We study the effect of defects on the dynamics of quasi-one-dimensional magnetic domain by simulation. In the present study, the system is composed of a ferromagnetic nanostripe and four symmetric defects.The magnetization of the nanostripe is assumed to be pinned at the two end, and it contains a single domain wall.We use the spin polarized current flowed in the plane driving the domain wall motion.There are two stable states of magnetization due to defects.The different current density values and directions let the magnetization be transformed between the two stable states.We find that the domain wall was rebounded when the current was switched off.And the rebounding phenomenon appears only if the current density j is greater than j_criticle and the fall time is less than 2x10^9 second. The phenomenon could be used in STT-based devices because the domain wall location could be controlled by the direct current and the devices could be simpler.