Nanofabrication and Applications of Domain Structures and Devices in Novel Magnetic Multilayers(III)

[[abstract]]本年為三年期整合型計畫的最後一年，在過去三年研究期間，我們持續探討微磁學相關的部分，除了靜態磁區的形成與分佈，同時透過磁阻的量測，進一步的探討了主要內容涵蓋如下：透過磁力顯微儀探究奈米級磁性薄膜之磁區結構；經由磁阻量測微米級鎳鐵環的磁區動態行為；磁性多層膜之穿遂磁阻行為。尤其結合多年來對鎳鐵單層環的磁區結構瞭解，我們成功的解釋發生於磁性多層膜穿遂結相關現象。 尤其對鎳鐵環的研究，我們不僅對磁矩分佈有更進一層的認識，尤其洋蔥態及漩渦態及其相混和態的形成時機，更對尺寸效應對磁矩動態翻轉的影響有很深的瞭解與掌控，就是有關直徑、線寬、及磁膜厚度相關之上述現象也完全掌握。更進一部以電流誘致之方式特意操空磁矩動態行為，相信會有很好的未來發展。另外，對於環狀的穿遂多層膜元件的研究有豐盛的成果，我們發表了全世界第一個成功的環元件，對於一個記憶元件具有多重態的發現，相信有助於提升記憶元密度的潛力。[[abstract]]During the last three years of joint project, the micro-magnetism-related subjects have been continually studied in this sub-areas of as follow: magnetization configuration and it’s evolution under external magnetic field on micro-structured permalloy ring devices; dynamic behaviors were investigated through magnetoresistance measurements; studies on the microstructured tunnel junctions in the multilayer magnetic films, especially with the ring-shaped devices. With the knowledge accumulated in the past we have successfully interpreted the reversal behavior in the magnetic tunnel junction rings. In the first subject, we have thoroughly studied the formation of vortex, onion, and metastable states in the permalloy ring devices. Furthermore, the dynamic behavior of magnetization subjected to external magnetic field has also been investigated through magnetic force microscopy and magnetoresistacne measurements. The size dependent of the domain configurations as well as the transition fields of vortex-to-onion and onion-to-vortex have been worked out in terms of the ring diameter, linewidth, and the thickness. Best of all, we have also studied the ring magnetization reversal by using current-induced magnetic field, i.e. with a current running through the ring center, which may offer an alternative and as best way of read/write technique in the field of magneto-resistive random access memory. We have, for the first time in the world, reported the ring-shaped magnetic tunnel junction. The main subject is to work out the reversal behaviors that may give us a better idea of further applications out of this subject. Indeed, the multiple meta-stable states occurred in the reversal regions have shown promising potential for ultrahigh density of magnetic storage