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Liu L, Ren Y, Robert W, Wang L, Wang X, Yang C. Terahertz wave radiation simulation in the Fe thin film. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:305902. [PMID: 38653257 DOI: 10.1088/1361-648x/ad4222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 04/23/2024] [Indexed: 04/25/2024]
Abstract
Femtosecond laser (FL) induced terahertz (THz) source is a new type of THz source based on injecting FL beams into ferromagnetic thin films by nonlinear effects to generate THz wave. It has a wider bandwidth compared to the traditional THz source, which provides higher flexibility and tunability in the application. In this paper, the three-temperature model and the stochastic Landau Lifshitz Gilbert equation at the atomic level are applied to simulate THz wave generation in Fe thin film induced by FL. Simulation results show that under a FL irradiance of 2 J m-2, the maximum demagnetization of the Fe thin film reaches 8.7%. The electromagnetic waves generated completely cover the THz band (0.1-10 THz), which fully satisfied the application requirements of the THz technology, verifying the feasibility of FL inducing the Fe thin film as a THz source. However, when the Fe thin film is overheated, it will be difficult for FL to excite valuable THz waves. Therefore, additional cooling devices are needed to keep the THz source in a workable temperature state, or to use ferromagnetic materials with magnetic moments that can quickly recover to saturation.
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Affiliation(s)
- Liwang Liu
- School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, People's Republic of China
| | - Yifan Ren
- Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei 230031, People's Republic of China
- Science Island Branch, Graduate School of University of Science and Technology of China, Hefei 230026, People's Republic of China
| | - Wieser Robert
- School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, People's Republic of China
| | - Lu Wang
- School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, People's Republic of China
| | - Xuan Wang
- Department of Physics, School of Science, Lanzhou University of Technology, Lanzhou 730050, People's Republic of China
| | - Cuihong Yang
- School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, People's Republic of China
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Pankratova M, Miranda IP, Thonig D, Pereiro M, Sjöqvist E, Delin A, Scheid P, Eriksson O, Bergman A. Coupled atomistic spin-lattice simulations of ultrafast demagnetization in 3d ferromagnets. Sci Rep 2024; 14:8138. [PMID: 38584162 PMCID: PMC10999457 DOI: 10.1038/s41598-024-58662-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 04/02/2024] [Indexed: 04/09/2024] Open
Abstract
Despite decades of research, the role of the lattice and its coupling to the magnetisation during ultrafast demagnetisation processes is still not fully understood. Here we report on studies of both explicit and implicit lattice effects on laser induced ultrafast demagnetisation of bcc Fe and fcc Co. We do this using atomistic spin- and lattice dynamics simulations following a heat-conserving three-temperature model. We show that this type of Langevin-based simulation is able to reproduce observed trends of the ultrafast magnetization dynamics of fcc Co and bcc Fe. The parameters used in our models are all obtained from electronic structure theory, with the exception of the lattice dynamics damping term, where a range of parameters were investigated. It was found that while the explicit spin-lattice coupling in the studied systems does not impact the demagnetisation process notably, the lattice damping has a large influence on the details of the magnetization dynamics. The dynamics of Fe and Co following the absorption of a femtosecond laser pulse are compared with previous results for Ni and similarities and differences in the materials' behavior are analysed. For all elements investigated so far with this model, we obtain a linear relationship between the value of the maximally demagnetized state and the fluence of the laser pulse , which is in agreement with experiments. Moreover, we demonstrate that the demagnetization amplitude is largest for Ni and smallest for Co. This holds over a wide range of the reported electron-phonon couplings, and this demagnetization trend is in agreement with recent experiments.
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Affiliation(s)
- M Pankratova
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden.
| | - I P Miranda
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden.
| | - D Thonig
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
- School of Science and Technology, Örebro University, 701 82, Örebro, Sweden
| | - M Pereiro
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - E Sjöqvist
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
| | - A Delin
- Department of Applied Physics, School of Engineering Sciences, KTH Royal Institute of Technology, AlbaNova University Center, 10691, Stockholm, Sweden
- Swedish e-Science Research Center (SeRC), KTH Royal Institute of Technology, 10044, Stockholm, Sweden
- Wallenberg Initiative Materials Science for Sustainability (WISE), KTH Royal Institute of Technology, 10044, Stockholm, Sweden
| | - P Scheid
- LPCT, CNRS, UMR 7019, BP 70239, Université de Lorraine, 54506, Vandoeuvre-lés-Nancy Cedex, France
- IJL, CNRS, UMR 7198, BP 70239, Université de Lorraine, 54000, Nancy Cedex, France
| | - O Eriksson
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
- Wallenberg Initiative Materials Science for Sustainability, Uppsala University, 75121, Uppsala, Sweden
| | - A Bergman
- Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
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