Multiscale dynamics of helicity-dependent all-optical magnetization reversal in ferromagnetic Co/Pt multilayers

Journal article (2017)

Authors

Rajasekhar Medapalli University of California
D. Afanasiev Radboud Universiteit Nijmegen, QN/Caviglia Lab - AS , Kavli institute of nanoscience Delft
D. Kim University of California
Y. Quessab Lorraine University, University of California
S. Manna University of California
S. A. Montoya University of California
A. Kirilyuk Radboud Universiteit Nijmegen
Th Rasing Radboud Universiteit Nijmegen
A. V. Kimel Radboud Universiteit Nijmegen, Moscow Technological University,
E. E. Fullerton University of California
Research Group
QN/Caviglia Lab (AS) (TU Delft)
Copyright: © 2017 R. Medapalli, D. Afanasiev, D. Kim, Y. Quessab, S. Manna, S. A. Montoya, A. Kirilyuk, Th Rasing, A. V. Kimel, E. E. Fullerton
DOI: https://doi.org/10.1103/PhysRevB.96.224421
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Published Date

2017

Language

English

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Faculty

Applied Sciences

Department

QN/Quantum Nanoscience

Research Group

QN/Caviglia Lab

Abstract

Time-resolved magneto-optical imaging reveals that the dynamics of the helicity-dependent all-optical switching (HD-AOS) of Co/Pt ferromagnetic multilayers occurs on the time scales from nanoseconds to seconds. We find HD-AOS proceeds by two stages. First, for an optimized laser fluence, the ultrashort laser pulse demagnetizes the film to 25% of the initial magnetization. Subsequent laser pulses aids nucleation of small reversed domains. The observed nucleation is stochastic and independent of the helicity of laser light. At the second stage circularly polarized light breaks the degeneracy between the magnetic domains promoting a preferred direction of domain wall motion. One circular polarization results in a collapse of the reversed magnetic domains. The other polarization causes the growth of reversed magnetic domain from the nucleation sites, via deterministic displacement of the domain wall resulting in magnetization reversal. This mechanism is supported by further imaging studies of deterministic laser-induced displacement of the domain walls when excited by circularly polarized optical pulses.

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