Femtosecond Optical Control of Magnetism: from fundamentals to submicron dynamics
Femtosecond Optical Control of Magnetism: from fundamentals to submicron dynamics
A. V. Kimel
Radboud Universiteit Nijmegen
The demand for the ever-increasing speed of information storage and manipulation has triggered an intense search for ways to control the magnetization in nanostructures by means other than magnetic fields. The control of magnetism by light is one of the promising approaches to this problem, because such methods may access timescales of a picosecond (10-12 sec) or less [1]. However, the realization of the latter requires answering several fundamental questions:
What is the The demand for the ever-increasing speed of information storage and manipulation has triggered an intense search for ways to control the magnetization in nanostructures by means other than magnetic fields. The control of magnetism by light is one of the promising approaches to this problem, because such methods may access timescales of a picosecond (10-12 sec) or less [1]. However, the realization of the latter requires answering several fundamental questions:
What is the mechanism of the efficient spin-light coupling?
What are the possible scenarios of magnetization reversal if it is triggered by a subpicosecond stimulus?
Can all-optical magnetization reversal operate at the nanoscale?
In my lecture I would like to discuss these questions. In particular, I will show that mechanisms of magnetic switching triggered by such an excitation can be very counterintuitive [2,3]. For example, until now it has been generally assumed that heating alone, not represented as a vector at all, cannot result in a deterministic reversal of magnetization, although it may assist this process. Here we will demonstrate a novel mechanism of deterministic magnetization reversal in a ferrimagnet driven by an ultrafast laser-induced heating of the medium without the presence of a magnetic field [3]. The mechanism is demonstrated for continuous films as well as for microstructures with in-plane and out-of-plane magnetic anisotropy. Peculiarities of ultrafast optical control of magnetism in magnetic structures with sizes down to 200 nm will be discussed [4,5]. It will be also shown that employing plasmonic nano-antennas it should be possible to confine opto-magnetic excitation in a spot well below diffraction limit, making ultrafast all-optical magnetic data recording achievable [6]
[1] A. Kirilyuk, A. V. Kimel and Th. Rasing, Rev. Mod. Phys. 82, 2731 (2010).
[2] I. Radu, K. Vahaplar, C. Stamm, T. Kachel, N. Pontius, H. A. Durr, T. A. Ostler, J. Barker, R. F. L. Evans, R. W. Chantrell, A. Tsukamoto, A. Itoh, A. Kirilyuk, Th. Rasing, and A. V. Kimel, Nature 472 205-208 (2011).
[3] T.A. Ostler, J. Barker, R.F.L. Evans, R.W. Chantrell, U. Atxitia, O. Chubykalo-Fesenko, S. El Moussaoui, L. Le Guyader, E. Mengotti, L.J. Heyderman, F. Nolting, A. Tsukamoto, A. Itoh, D. Afanasiev, B.A. Ivanov, A.M. Kalashnikova, K. Vahaplar, J. Mentink, A. Kirilyuk, Th. Rasing and A.V. Kimel, Nature-Communications 3: 666 (2012).
[4] M. Savoini, R. Medapalli, B. Koene, A. R. Khorsand, L. Le Guyader, L. Duo, M. Finazzi, A. Tsukamoto, A. Itoh, F. Nolting, A. Kirilyuk, A. V. Kimel and Th. Rasing, Phys. Rev. B 86, 140404(R) (2012).
[5] L. Le Guyader, S. El Moussaoui, M. Buzzi, R. V. Chopdekar, L. J. Heyderman, A. Tsukamoto, A. Itoh, A. Kirilyuk, Th. Rasing, A. V. Kimel and F. Nolting, Appl. Phys. Lett. 101, 022410 (2012).
[6] B. Koene, M. Savoini, A. V. Kimel, A. Kirilyuk, and Th. Rasing, Appl. Phys. Lett.101, 013115 (2012).