BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Memento EPFL// BEGIN:VEVENT SUMMARY:IMX Seminar Series - Ultrafast magnetism – terra incognita beyon d the classical approximations DTSTART:20240513T131500 DTEND:20240513T141500 DTSTAMP:20260427T201434Z UID:d28878762bed6ba47416e67747f5d62d55e68154c3b0ea5dae20e2a4 CATEGORIES:Conferences - Seminars DESCRIPTION:Prof. Alexei V. Kimel\, Radboud University\, Netherlands\nWhil e magnetism is practically the strongest quantum mechanical phenomenon\, m odern description of magnetization dynamics and magnetization reversal rel ies on thermodynamics and the corresponding approximations. I will show th at ultrashort (sub-100 ps) stimuli push magnetic media into a strongly non equilibrium state\, where the conventional description of magnetic phenom ena in terms of equilibrium thermodynamics fail and the experimentally obs erved ultrafast magnetization dynamics and reversal challenge the current theories. For instance\, while the conventionally accepted Curie-Neumann ’s principle states that “the symmetries of the causes are to be found in the effects" [1]\, in ultrafast magnetism the principle fails and magn etization dynamics becomes counter-intuitive.\n\nIn my talk\, I will discu ss two main examples of such counter-intuitive spin dynamics:\n\n1) While according to thermodynamics and simply intuition\, heat can only destroy m agnetization\, we will demonstrate that ultrafast (sub-100 ps) heat pulse can cause magnetization reversal without any magnetic fields [2].\n2) Whil e control of spins in antiferromagnets requires increasingly high magnetic fields\, rapidly varying magnetic field at THz rates is a game-changer in the field. Picosecond pulses of THz magnetic field with the strength belo w 1 T can efficiently excite spins in antiferromagnets and even push spin dynamics into nonlinear regime\, where new channels of spin-lattice intera ction open-up [3] and the principle of superposition fails i.e. 1+1>2 [4]. \n\n[1] P. Curie\, J. Phys. Theor. Appl.\, 393-415(1894).\n[2] T.A. Ostler et al\, Ultrafast heating as a sufficient stimulus for magnetization reve rsal in a ferrimagnet\, Nature-Communications 3\, 666 (2012).\n[3] E. A. M ashkovich et al\, THz light driven coupling of antiferromagnetic spins to lattice\, Science 374\, 1608-1611 (2021).\n[4] T. G. H. Blank et al\, Empo wering control of antiferromagnetic spins by THz spin coherence\, Phys. Re v. Lett. 131\, 096701 (2023).\n\nBio: In 2002 he obtained his PhD from the Ioffe institute (St. Petersburg\, Russia) and joined Radboud University a s a postdoc\, where he became later an assistant professor (2007)\, associ ate professor (2013) and full professor (2017). He pioneered ultrafast spi n dynamics in antiferromagnetic materials already 20 years ago [PRL89\, 28 7401 (2002)\, Nature 435 655–657 (2005)] and his works in a large extent defined the development of ultrafast magnetism during the last two decade s. He is a co-inventor of ultrafast all-optical magnetic recording [PRL99\ , 047601 (2007)] and inertia of spins in antiferromagnets [Nature-Physics5 \, 727–731 (2009)]\, as a recognized world-leader in the field he obtain ed several prestigious research grants (Veni2004\, Vidi2006\, Vici2017\, E RC-SG2010\, Russian MegaGrant-2013\, ERC-AG2022). During the last years\, his group has been pushing the frontiers of the field demonstrating the fa stest and the least dissipative magnetic switching [Nature 542\, 71–74 ( 2017)]\, revealing temporal and spectral fingerprints of the coherent swit ching in antiferomagnets [Nature 569\, 7756 (2019)]\, discovering the regi me of highly anharmonic dynamics of antiferromagnetic spins [Science 374 1 608-1611 (2021)\, PRL (2023)]. LOCATION:MXF 1 https://plan.epfl.ch/?room==MXF%201 STATUS:CONFIRMED END:VEVENT END:VCALENDAR