Introduction

Abstract

This thesis addresses the current-driven magnetic domain wall (DW) motion in antiferromagnetically-coupled ferrimagnets. There are two aspects behind this topic: current-driven DW motion in ferromagnetic materials, which has been an area of intense research for several decades, and antiferromagnetic-like dynamics of ferrimagnets, which has been recently attracting increasing attention. Because ferrimagnets and antiferromagnets are expected to exhibit advantageous characteristics, such as the ultrafast spin dynamics, for device applications, it is necessary to clarify the current-driven ferrimagnetic/antiferromagnetic dynamics. This chapter introduces the physics required to understand the main results of this thesis. In particular, the current-driven DW motion is explained in Sect. 1.1, and two mechanisms of the current-driven DW motion, namely, the spin-transfer torque (STT) and spin–orbit torque (SOT), are described in detail. In Sect. 1.2, spin-torque ferromagnetic resonance, which is a type of ferromagnetic resonance excited by SOT, is introduced. This is used as an experimental method in Chap. 4. In Sect. 1.3, recent studies on ferrimagnetic DW motion are summarized. In addition to helping in understanding the physical backgrounds of this thesis. This chapter also introduces readers to one of the recent topics of the spintronic research field.KeywordsCurrent-driven magnetic domain wall motionSpin-torque ferromagnetic resonanceAntiferromagnetically-coupled ferrimagnets