Ultrafast changes of magnetic anisotropy driven by laser-generated heat and strain in low-symmetry films
Alexandra M. Kalashnikova (Ferroics Physics Laboratory, Ioffe Institute of RAS, St. Petersburg, Russia)

Femtomagnetism is the emerging field in condensed matter physics, aiming at understanding microscopical mechanisms defining the response of a magnetic matter and nanostructures to short and intense optical excitation [1] and developing novel approaches to control the magnetic state on pico- and subpicosecond time scales. By now it is understood that the laser-induced dynamics of magnetization results from interplay between processes in electronic, phononic and spin subsystems triggered by femtosecond optical pulses. In this talk we consider the problem of the laser-induced changes of magnetic anisotropy of magnetic metallic and dielectric films, which can serve as an effective way to trigger and control the dynamics of magnetization.
Among the magnetic dielectrics, in thin films of iron garnets is of particular interest, since these media are the model ones for the rapidly developing field of magnonics. Here we present the results of experimental studies of the laser-induced dynamics in substituted iron garnet films grown on a (210) GGG-substrate, and demonstrate how the magnetic anisotropy in such a film can be controlled via picoseconds laser-induced increase of lattice temperature [2].
In magnetic metals laser-induced increase of the lattice temperature in response to femtosecond laser excitation is known to change effectively magnetocrystalline anisotropy [3]. On the other hand, thermal expansion of the lattice generates a dynamical strain. However, by now the contribution of the latter mechanism to the response of magnetic films to the direct optical excitation is not fully understood. Here, by studying experimentally and theoretically the laser-induced dynamics in a thin film of magnetostrictive metallic alloy Fe81Ga19 grown on a low-symmetry (311)-GaAs substrate we demonstrate how the contributions from these two coexisting mechanisms can be distinguished, and define the conditions at which these mechanisms dominate [4,5].
[1] A. Kirilyuk, A. V. Kimel, and T. Rasing, Rev. Mod. Phys. 82, 2731 (2010).
[2] L. A. Shelukhin, V. V. Pavlov, P. A. Usachev, R. V. Pisarev, A. M. Kalashnikova, arXiv:1507.07437.
[3] E. Carpene, E. Mancini, D. Dazzi, C. Dallera, E. Puppin, and S. De Silvestri, Phys. Rev. B 81, 060415 (2010).
[4] T. L. Linnik, V. N. Kats, J. Jäger, A. S. Salasyuk, D. R. Yakovlev, A. W. Rushforth, A. V. Akimov, A. M. Kalashnikova, M. Bayer, A. V. Scherbakov, Phys. Scr. 92, 054006 (2017).
[5] V. N. Kats, T. L. Linnik, A. S. Salasyuk, A. W. Rushforth, M. Wang, P. Wadley, S.A. Cavil, V. Holy, A. V. Akimov, A. M. Kalashnikova, A. V. Scherbakov, Phys. Rev. B 93, 214422 (2016).