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Switching by Domain-Wall Automotion in Asymmetric Ferromagnetic Rings

Mohamad-Assaad Mawass1,2,3, Kornel Richter1, Andre Bisig1,2, Robert M. Reeve1, Benjamin Krüger1, Markus Weigand2, Hermann Stoll2, Andrea Krone1, Florian Kronast3 et al.

Gisela Schütz2 and Mathias Kläui1,4

  • 1Johannes Gutenberg Universität-Mainz, Institut of Physics, Staudinger Weg 7, 55128 Mainz, Germany
  • 2Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany
  • 3Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
  • 4Graduate School of Excellence Materials Science in Mainz (MAINZ), Staudinger Weg 9, 55128 Mainz, Germany

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Phys. Rev. Applied 7, 044009 – Published 18 April, 2017

DOI: https://doi.org/10.1103/PhysRevApplied.7.044009

Abstract

Spintronic applications based on magnetic domain-wall (DW) motion, such as magnetic data storage, sensors, and logic devices, require approaches to reliably manipulate the magnetization in nanowires. In this paper, we report the direct dynamic experimental visualization of reliable switching from the onion to the vortex state by DW automotion at zero field in asymmetric ferromagnetic rings using a uniaxial field pulse. Employing time-resolved x-ray microscopy, we demonstrate that depending on the detailed spin structure of the DWs and the size and geometry of the rings, the automotive propagation can be tailored during the DW relaxation from the higher-energy onion state to the energetically favored vortex state, where both DWs annihilate. Our measurements show DW automotion with an average velocity of about 60  m/s, which is a significant speed for spintronic devices. Such motion is mostly governed by local forces resulting from the geometry variations in the device. A closer study of the annihilation process via micromagnetic simulations reveals that a new vortex is nucleated in between the two initial walls. We demonstrate that the annihilation of DWs through automotion in our scheme always occurs with the detailed topological nature of the walls influencing only the DW dynamics on a local scale. The simulations show good quantitative agreement with our experimental results. These findings shed light on a robust and reliable switching process of the onion state in ferromagnetic rings, which paves the way for further optimization of these devices.

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Phys. Rev. Applied 7, 044009– Published 18 April, 2017
  • Received 2 September 2016

© 2017 American Physical Society

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