Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 39: Focus Session: Unconventional Spin Structures (jointly with DS)

MA 39.1: Topical Talk

Donnerstag, 3. April 2014, 09:30–10:00, BEY 118

Topological Effects in Nanomagnetism - From Perpendicular Recording to Monopoles — •Hans-Benjamin Braun — University College Dublin

Similar to knots in a rope, the magnetization in a material can form particularly robust configurations. Such topologically stable structures include domain walls, vortices and skyrmions which are not just attractive candidates for future data storage applications but are also of fundamental importance to current memory technology. For example, the creation of soliton pairs of opposite chirality delimits the thermal stability of bits in current high anisotropy perpendicular recording media. After an introduction into various types of topological defects and their implications for current data storage it will be discussed how vortices can be robustly implemented in a system of nanoislands, a system that is in principle scaleable to the smallest length scales. It will then be shown how magnetic monopoles emerge as topological defects in densely packed arrays of nanoislands, a system also known as artificial spin ice. In contrast to conventional thin films, where magnetization reversal occurs via nucleation and extensive domain growth, magnetization reversal in 2D artificial spin ice is restricted to an avalanche-type formation of 1D strings. These objects can be viewed as classical versions of Dirac strings that feed magnetic flux into the emergent magnetic monopoles. It is demonstrated how the motion of these magnetic charges can be individually controlled experimentally and used to perform simple logic operations.