Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for +publisher:"ETH Zürich" +contributor:("id_orcid0000-0001-6074-4894"). Showing records 1 – 3 of 3 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


ETH Zürich

1. Tzschaschel, Christian. Coherent spin dynamics in optically excited antiferromagnets.

Degree: 2019, ETH Zürich

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. Advisors/Committee Members: Fiebig, Manfred, Satoh, Takuya, Johnson, Steven, id_orcid0000-0001-6074-4894.

Subjects/Keywords: info:eu-repo/classification/ddc/530; info:eu-repo/classification/ddc/620; Physics; Engineering & allied operations

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Tzschaschel, C. (2019). Coherent spin dynamics in optically excited antiferromagnets. (Doctoral Dissertation). ETH Zürich. Retrieved from http://hdl.handle.net/20.500.11850/379113

Chicago Manual of Style (16th Edition):

Tzschaschel, Christian. “Coherent spin dynamics in optically excited antiferromagnets.” 2019. Doctoral Dissertation, ETH Zürich. Accessed April 12, 2021. http://hdl.handle.net/20.500.11850/379113.

MLA Handbook (7th Edition):

Tzschaschel, Christian. “Coherent spin dynamics in optically excited antiferromagnets.” 2019. Web. 12 Apr 2021.

Vancouver:

Tzschaschel C. Coherent spin dynamics in optically excited antiferromagnets. [Internet] [Doctoral dissertation]. ETH Zürich; 2019. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/20.500.11850/379113.

Council of Science Editors:

Tzschaschel C. Coherent spin dynamics in optically excited antiferromagnets. [Doctoral Dissertation]. ETH Zürich; 2019. Available from: http://hdl.handle.net/20.500.11850/379113


ETH Zürich

2. Dornes, Christian. Ultrafast studies on the coupling of magnetic and structural dynamics in solid-state ferromagnets.

Degree: 2018, ETH Zürich

The thesis describes primarily two experiments which investigate the coupling of structural and magnetic properties in solid-state ferromagnets on an ultrafast (\approx100~fs) timescale. To achieve this goal, both studies use ultrafast optical and x-ray pump-probe methods in combination, integrating information about magnetic and structural dynamics to form a more complete picture of the underlying physics. In the first experiment, the well-known shape-memory ferromagnetic Heusler alloy {Ni}2{MnGa} is studied. This compound is a multiferroic material stabilised by the correlations between electronic, magnetic, and structural order. The shape-memory effect is based on a structural phase transition between a low-temperature martensite phase and a high-temperature austenite phase. In both phases, the material is ferromagnetic. It has been observed for different stoichiometries that the martensite phase exhibits slightly incommensurate structural modulations whenever the shape-memory effect is present, but the exact connection between the two is unclear. We performed ultrafast optical measurements of the magnetisation of {Ni}2{MnGa}, using 100~fs, 800~nm pulses for both the pump and the magneto-optical Kerr effect probe. We found a rapid demagnetisation with a timescale of 320±50~fs, followed by a very slow recovery. At the FEMTO slicing source, we performed ultrafast x-ray diffraction on the weak (20201) satellite reflection of the (202) Bragg peak, which is a measure of the structural modulation. At high fluences of the 800~nm near-IR pump, we were able to observe a rapid and almost complete suppression of the structural modulation on a timescale of 300±40~fs, very similar to the behaviour of the magnetisation. However, the longer timescale dynamics are markedly different from the one observed in the magnetisation: we observed an intermediate recovery of the structural modulation, before a second drop was caused by the thermal phase transition to the high-temperature austenite structure, which does not support the structural modulation. Our conclusion is that magnetisation and structural modulation are not strongly coupled in {Ni}2{MnGa}, as the structural modulation was able to recover even while the material was demagnetised. The second experiment studied the movement of the lattice during ultrafast demagnetisation of a thin single-crystal iron film. While ultrafast demagnetisation is a very well-established effect, its microscopic mechanism remains unclear, especially with respect to the flow of angular momentum. Our goal was therefore to find a signature of the ultrafast Einstein – De Haas effect, i.e. the flow of spin angular momentum from the magnetisation to the mechanical angular momentum of the lattice. We identified that transverse shear waves would be launched from the surfaces of a rapidly demagnetising crystal, with an initial deflection whose direction depends on the magnetisation. A double-grazing x-ray diffraction geometry to measure the crystal… Advisors/Committee Members: Johnson, Steven, id_orcid0000-0001-6074-4894, Acremann, Yves Marc, id_orcid0000-0002-4109-3544, Pontius, Niko.

Subjects/Keywords: Ultrafast optics; Ultrafast magnetization dynamics; X-ray diffraction; Multiferroics; Iron; Ultrafast demagnetization; Angular momentum; info:eu-repo/classification/ddc/530; info:eu-repo/classification/ddc/530; Physics; Physics

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Dornes, C. (2018). Ultrafast studies on the coupling of magnetic and structural dynamics in solid-state ferromagnets. (Doctoral Dissertation). ETH Zürich. Retrieved from http://hdl.handle.net/20.500.11850/331285

Chicago Manual of Style (16th Edition):

Dornes, Christian. “Ultrafast studies on the coupling of magnetic and structural dynamics in solid-state ferromagnets.” 2018. Doctoral Dissertation, ETH Zürich. Accessed April 12, 2021. http://hdl.handle.net/20.500.11850/331285.

MLA Handbook (7th Edition):

Dornes, Christian. “Ultrafast studies on the coupling of magnetic and structural dynamics in solid-state ferromagnets.” 2018. Web. 12 Apr 2021.

Vancouver:

Dornes C. Ultrafast studies on the coupling of magnetic and structural dynamics in solid-state ferromagnets. [Internet] [Doctoral dissertation]. ETH Zürich; 2018. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/20.500.11850/331285.

Council of Science Editors:

Dornes C. Ultrafast studies on the coupling of magnetic and structural dynamics in solid-state ferromagnets. [Doctoral Dissertation]. ETH Zürich; 2018. Available from: http://hdl.handle.net/20.500.11850/331285


ETH Zürich

3. Volkov, Mikhail. Attosecond transient absorption spectroscopy of solids.

Degree: 2018, ETH Zürich

Subjects/Keywords: info:eu-repo/classification/ddc/540; info:eu-repo/classification/ddc/530; Chemistry; Physics

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Volkov, M. (2018). Attosecond transient absorption spectroscopy of solids. (Doctoral Dissertation). ETH Zürich. Retrieved from http://hdl.handle.net/20.500.11850/312656

Chicago Manual of Style (16th Edition):

Volkov, Mikhail. “Attosecond transient absorption spectroscopy of solids.” 2018. Doctoral Dissertation, ETH Zürich. Accessed April 12, 2021. http://hdl.handle.net/20.500.11850/312656.

MLA Handbook (7th Edition):

Volkov, Mikhail. “Attosecond transient absorption spectroscopy of solids.” 2018. Web. 12 Apr 2021.

Vancouver:

Volkov M. Attosecond transient absorption spectroscopy of solids. [Internet] [Doctoral dissertation]. ETH Zürich; 2018. [cited 2021 Apr 12]. Available from: http://hdl.handle.net/20.500.11850/312656.

Council of Science Editors:

Volkov M. Attosecond transient absorption spectroscopy of solids. [Doctoral Dissertation]. ETH Zürich; 2018. Available from: http://hdl.handle.net/20.500.11850/312656

.