Coherent spin dynamics in optically excited antiferromagnets
OPEN ACCESS
Author / Producer
Date
2019-11
Publication Type
Doctoral Thesis
ETH Bibliography
yes
Citations
Altmetric
OPEN ACCESS
Data
Rights / License
Abstract
Antiferromagnetic spintronics emerged in the last decade as a promising approach to overcome limitations of current information technology. Owing to the vanishing net magnetization, antiferromagnetic materials exhibit spin dynamics on sub-picosecond timescales potentially allowing not only for data storage and logic circuit applications that are orders of magnitude faster than their established ferromagnetic counterparts, but also the development of new paradigms for device architectures with greater functionality. Due to a tremendous interest in the realization of antiferromagnet-based devices, the tools for the ultrafast control and manipulation of antiferromagnets are currently being explored.
In the current thesis, we use time-resolved optical experiments to unravel the coherent spin dynamics in antiferromagnets on their intrinsic timescales. Three consecutive projects form the cornerstones of the present cumulative thesis. In the first project, we achieved for the first time the experimental discrimination of different spin excitation mechanisms. The fundamental understanding of the relevant excitation mechanism constitutes an unprecedented degree of optical control of antiferromagnets. The second project is concerned with probing antiferromagnetic spin dynamics. We show that time-resolved measurements of optical second-harmonic generation provide quantitative access directly to the antiferromagnetic order parameter. In combination with established magneto-optical probes, we track the motion of an antiferromagnetic order parameter in three dimensions. We find that the spin precession during an antiferromagnetic resonance exhibits a pronounced ellipticity, which opens up new routes for the energy efficient control of antiferromagnetic order. Lastly, we show that spin damping during the optical excitation gives rise to an optically induced ferromagnetic spin canting in otherwise fully compensated antiferromagnets. We show that this process, which has so far been neglected for ultrafast optical excitations, can be the dominant spin excitation mechanism in antiferromagnets.
The results of this thesis provide new insights into the optical control and manipulation of antiferromagnets. These key findings are crucial for the development of future antiferromagnetic spintronic devices.
Beyond academic research, the present thesis also constitutes an educational advancement. In an effort to improve our capabilities of teaching X-ray diffraction techniques to undergraduate students, an intuitive and flexible device is presented in the appendix.
Permanent link
Publication status
published
External links
Editor
Contributors
Book title
Journal / series
Volume
Pages / Article No.
Publisher
ETH Zurich
Event
Edition / version
Methods
Software
Geographic location
Date collected
Date created
Subject
Organisational unit
03918 - Fiebig, Manfred / Fiebig, Manfred
Notes
Funding
Related publications and datasets
Is supplemented by: http://hdl.handle.net/20.500.11850/379246