Femtomagnetism: From laser-induced femtosecond demagnetization to all-optical spin switching

日期:2017-12-20 阅读:535


Magnetic recording has a market share of 10 billion dollars. Femtomagnetism started with the ground-breaking experiment by Beaurepaire and Bigot group in France. They discovered that an ultrashort laser pulse could reduce the magnetic spin moment of fcc Ni within 1 ps. Such a surprising finding challenges the traditional spin wave theories of any kinds. Even more puzzling is how the laser is capable of affecting spin degree of freedom. A similar scenario occurs in superconductors and other complex magnets. This field has expanded into all-optical spin reversal, where one does not need a magnetic field to switch spin. This talk is a short introduction to femtomagnetism, with emphasis on the latest developments in ultrafast magnetic storage on several hundred nanometer scales and all-optical switching devices for wireless communication. I will follow the history of femtomagnetism, and present a roadmap to the future.
1. E. Beaurepaire, J. -C. Merle, A. Daunois and J.-Y. Bigot, Ultrafast spin dynamics in ferromagnetic nickel, Phys. Rev. Lett. {\bf 76}, 4250 (1996).
2. G. P. Zhang and W. H\"ubner, Laser-induced ultrafast demagnetization in ferromagnetic metals, Phys. Rev. Lett.  {\bf 85}, 3025 (2000).
3. G. P. Zhang, W. H\"ubner, E.  Beaurepaire and J.-Y. Bigot, {\it Laser-induced ultrafast demagnetization: Femtomagnetism, A new frontier?}  Topics Appl. Phys.  {\bf 83}, 245-289 (2002).
4. G. P. Zhang, W. H\"ubner, Georgios Lefkidis, Yihua Bai, and T. F. George, Paradigm of the time-resolved magneto-optical Kerr effect for femtosecond magnetism, Nature Physics {\bf 5}, 499, (2009).
5. G. P. Zhang, Y. H. Bai and T. F. George, {\it Switching ferromagnetic spins by an ultrafast laser pulse: Emergence of giant optical spin-orbit torque}, EPL {\bf 115}, 57003 (2016).
6. Yuhang Ren, Wei Lai, Zehra Cevher, Yu Gong, and G. P. Zhang, {\it Experimental demonstration of 55-fs spin canting in photoexcited iron nanoarrays},  Appl. Phys. Lett. {\bf 110}, 082404 (2017).
7. G. P. Zhang, T. Jenkins, M. Bennett and Y. H. Bai, {\it Manifestation of intra-atomic 5d6s-4f exchange coupling in photoexcited gadolinium }, J. Phys.: Condens. Matter {\bf 29}, 495807 (2017).


Prof. Zhang obtained his B.Sc. in Nanjing Normal University, (1987), then he earned his M.Sc. in Shanghai Jiao-Tong University, (1990) and his Ph.D. in Fudan University, (1995). He carried postdoctoral research at the University of Tennessee (1999-2001) and Max-Planck Institute of Microstructure Physics (1997-1999). He joined the Faculty at Indiana State University, where he is currently a Professor of Physics, since 2002. Prof. Zhang has 112 peer-reviewed research articles published in ultrafast dynamics, nanostructures, femtomagnetism, strongly correlated electrons, interfaces and xray spectroscopy, with 11 in Physical Review Letters and 1 in Nature Physics, 3 books and 11 review chapters.

Host: Prof. Wei Ku


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