Study of nanoscale magnetization dynamics and reversal following ultrafast optical excitation by resonant X-ray diffraction
Abstract/Contents
- Abstract
- In 1996, femtosecond (fs) optical laser pulse was first discovered by as one of the novel methods to quench the magnetization[1]. While the fs optical laser pulses typically induces demagnetization, they are also discovered to be able to cause all-optical switching (AOS) of magnetic domains in the transition metal-rare earth (TM-RE) alloy GdFeCo[2, 3, 4, 5, 6]. This phenomenon not only opened door for fascinating non-equilibrium magnetism research but also brought forth the possibility of optical control of magnetism in future magnetic recording technologies. In this thesis, we take an microscopic approach to study the optically-induced magnetization dynamics by utilizing x-ray diffraction technique. We are able to address some important physics questions and technological relevancy regarding the phenomenon. The technological potential of AOS has recently increased with the discovery of the same effect in other materials, including RE-free magnetic multilayers[7, 8]. However, to be technologically competitive for the bit density requirement of future storage device, AOS must further restrict its optically-switched magnetic areas to sizes well below the diffraction limit. By deploying gold plasmonic antenna structure on the surface of ferrimagnetic TbFeCo alloy, we demonstrate reproducible and robust all-optical switching of magnetic domains of 53 nm size. The nanoscale magnetic reversal is imaged both around and beneath plasmonic antennas using x-ray resonant holographic imaging technique. Furthermore, our results also demonstrate the importance of the sample chemical nanostructure on the magnetic switching. The microscopic dynamics of magnetization following an fs optical excitation is also studied in the similar material GdFeCo. Based on theoretical predictions[9, 10], we searched for magnetic solitons generated from spin wave condensation in the far-from-equilibrium condition induced by fs optical excitation. By studying the resonant x-ray diffraction pattern, we present evidence of such soliton feature formation in magnetization dynamics experimentally. We also relate the microscopic magnetization picture to the bulk magnetization response of the sample.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2017 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Liu, Tianmin |
|---|---|
| Associated with | Stanford University, Department of Physics. |
| Primary advisor | Stöhr, Joachim |
| Thesis advisor | Stöhr, Joachim |
| Thesis advisor | Kasevich, Mark A |
| Thesis advisor | Reis, David A, 1970- |
| Advisor | Kasevich, Mark A |
| Advisor | Reis, David A, 1970- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | TianMin Liu. |
|---|---|
| Note | Submitted to the Department of Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2017. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2017 by TianMin Liu
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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