라시바 스핀-궤도 상호작용계에서의 자화동역학

Abstract

Spintronics is an extension of electronics using not only charge but also spin degree of freedom of electrons. In magnetic nanostructure, one can measure and control magnetization by using spin current and magnetic exchange interaction. In this sense, studying magnetization dynamics under external electromagnetic field provides central theoretical concepts of spintronics.Considering that magnetic nanostructures are getting increasingly miniaturized, studying magnetization dynamics in thin (∼1nm) film nanostructure becomes important. Recent experimental reports imply that magnetization dynamics in thin film structure is not simply given by thin limit of thicker counterpart. In such systems, it is known that inversion symmetry breaking causes strong spin-orbit coupling effect of Rashba type, so magnetization dynamics can be qualitatively modified. Therefore, studying magnetization dynamics in the presence of Rashba spin-orbit coupling is very important.There are two important physics when studying magnetization dynamics. One is spin-transfer torque, which describes spin-current-induced magnetization dynamics, and the other is spin motive force, which describes magnetization-dynamics-induced spin current. In real system, these two phenomena couple with each other, therefore, it is important to study not only spin-transfer torque and spin motive force separately, but also coupling of them. For instance, magnetization dynamicsinduces spin current by spin motive force, and this spin current affect magnetization itself by spin-transfer torque. This self-feedback is one of very important features of this thesis.The thesis consists of two parts. Part I and II focus respectively on spin-transfer torque and spin motive force. Result of the self-feedback is included in Part II.