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180° transverse domain walls (TDWs) in planar magnetic nanowires find important applications in advanced logic and memory devices. Controlling DW structure is important because it determines DW behaviors and is used to store digital information. This paper presents, using micromagnetic simulations, simple designs of nanowire unit that enables reliable generation of TDWs and effective control of their structures under rotating magnetic field. It is shown that a series of TDWs can be created, two per loading cycle, and external magnetic field can be programmed to control the TDW structures in terms of their polarity and chirality. These nanowire units and the corresponding magnetic field control schemes can be integrated into magnetic circuits to generate TDWs of controlled structures, facilitating the development of logic and memory devices based on DW functionalities. [ABSTRACT FROM AUTHOR]

We report a new type of racetrack memory based on current-controlled movement of magnetic vortices in magnetic nanowires with rectangular cross-section and weak perpendicular anisotropy. Data are stored through the core polarity of vortices and each vortex carries a data bit. Besides high density, non-volatility, fast data access, and low power as offered by domain wall racetrack memory, magnetic vortex racetrack memory has additional advantages of no need for constrictions to define data bits, changeable information density, adjustable current magnitude for data propagation, and versatile means of ultrafast vortex core switching. By using micromagnetic simulations, current-controlled motion of magnetic vortices in cobalt nanowire is demonstrated for racetrack memory applications. [ABSTRACT FROM AUTHOR]

An important role of domain wall pile-up in current-driven domain wall depinning in magnetic nanowires is revealed using micromagnetic simulations. It is found that the critical current for domain wall depinning can be substantially reduced and conveniently tuned by controlling domain wall number in the pile-up at pinning site, in analogy to dislocation pile-up responsible for Hall–Petch effect in mechanical strength. Domain wall pinning and depinning at an s-shape bend is considered, and the effects of curvature and current crowding in magnetic circuit on domain wall behaviors are discussed. [ABSTRACT FROM AUTHOR]